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Model PIM-3 12-1

Chapter 12

Understanding Limits

12.1 Introduction

The manner in which limits detectors operate can be

confusing because terminology differs from manufacturer
to manufacturer. This section will define what SENSO-
TEC means when statements are made regarding limits.

12.2 Definitions

LIMITS -- Comparators which detect that a signal
does or does not exceed a pre-established refer-
ence value.

FAIL-SAFE -- A configuration of limits such that
normal operation never produces the same condition
produced by power failure.

LOW LIMIT -- A limit configuration in which the limit
is tripped when the signal is less than the limit
reference setting.

HIGH LIMIT -- A limit configuration in which the limit
is tripped when the signal is more than the limit
reference setting.

HYSTERESIS -- A deadband in which a tripped
limit will not deenergize. This makes the limit noise-
resistant up to the amount of the hysteresis.

Содержание PIM-3

Страница 1: ...2080 Arlingate Lane Columbus Ohio 43228 614 850 5000 DIGITAL INLINE AMPLIFIER MODEL PIM 3 ...

Страница 2: ... Sensotec Part Number 008 0239 00 Rev E November 1997 Copyright Notice Copyright 1995 by Sensotec Inc 2080 Arlingate Lane Columbus OH 43228 U S A All Rights Reserved Printed in U S A Trademarks PIM 3 is a trademark of SENSOTEC INC ...

Страница 3: ...Bits and Parity 6 1 6 2 Special Order Instruments 6 2 6 3 Two Types of Commands 6 2 6 4 Addressing 6 2 6 5 Command Format 6 3 6 6 Response Format 6 5 CHAPTER 7 RS 232 Installation Notes 7 1 Introduction 7 1 7 2 Function of Pins 7 1 7 3 Operation Notes 7 1 7 4 Typical Wiring Diagrams 7 2 CHAPTER 8 RS 485 Installation Notes 8 1 Introduction 8 1 8 2 Installation Overview 8 1 8 3 Function of Pins 8 3 ...

Страница 4: ... 10 8 WJ Write Automatic Limit Report 10 9 10 9 WI Write Continous Transmit Setting 10 10 10 10 RR Read Software Revision 10 11 CHAPTER 11 Amplifier Commands 11 1 F0 Transmit Data 11 2 11 2 F1 Activate Tare Zero 11 3 11 3 F2 Clear Tare Zero 11 4 11 4 F3 Calilbrate Analog to Digital Converter 11 5 11 5 F4 Calibrate Amplifier using Shunt Cal Method 11 6 11 6 F5 Apply Shunt Resistor and Transmit Read...

Страница 5: ... 12 1 12 3 Configuring Limits 12 2 CHAPTER 13 Calibration Examples 13 1 Known Load Calibration Example 13 1 13 1 1 Introduction 13 1 13 1 2 Requirements 13 1 13 1 3 Calibration Example 13 1 13 2 Shunt Resistor Calibration Example 13 3 13 2 1 Introduction 13 3 13 2 2 Requirements 13 3 13 2 3 Calibration Example 13 4 13 3 Using a Single Transducer with Multiple PIM 3 s 13 3 APPENDIX A 1 Warranty and...

Страница 6: ...NOTES ...

Страница 7: ...mplifi ers and digital inline amplifiers is the fact that the output of the digital versions is a digital signal usually coded in ASCII characters Standards for serial data transmission such as RS 232 or RS 485 specify the signal transmis sion characteristics Because the digital inline amplifier is effectively a small computer the usual functions of an inline amplifier covered above can be increas...

Страница 8: ...ectors on the case of the PIM 3 and what the func tions are for each pin Chapter 5 Getting Started with the PIM 3 describes how to quickly establish that a PIM 3 is connected and operating properly Chapter 6 Command Format describes the soft ware protocol used by PIM 3 instruments which is the same for both RS 232 and RS 485 equipped PIM 3 s Chapter 7 RS 232 Installation Notes provides wir ing exa...

Страница 9: ...s describes in detail the commands that affect the communications and limit setup of the PIM 3 Chapter 11 Amplifier Commands describes in detail the commands that affect the operation of the trans ducer amplifier Chapter 12 Understanding Limits explains the setup and operation of the open collector limits and gives several setup examples Chapter 13 Calibration Examples provides exam ples of calibr...

Страница 10: ...1 4 Introduction ...

Страница 11: ...age 20 to 200 deg F Temperature Operating 0 to 150 deg F POWER REQUIREMENTS Power Supply Required 12 to 28 VDC 150mA TRANSDUCER INTERFACE SPECIFICATIONS Transducer Excitation 5 or 10 VDC Inputs Accepted 1 to 10 mV V Transducer Drive Max 30 mA Input Gain Range 20 to 200 Remote Shunt Cal Yes Calibration Method Shunt Resistor or Known Load Tare or Zero Balance 100 Noise and Ripple 83 db Transducer Mi...

Страница 12: ... 4800 9600 No of Characters Transmitted Up to 22 per message Scaling 999 999 maximum Eng Units Transmitted Yes up to 10 characters Polarity Indication Yes Decimal Point Selection Yes Overrange Indication Overrange Message Sent Resolution 1 part in 32 768 SPECIAL FEATURES Limit Outputs 4 Open Collector Outputs Command Table Over 35 Commands including 14 universals Analog Output optional 0 5 VDC or ...

Страница 13: ...ly controls the gain of the input amplifier 3 A D CONVERTER The analog to digital con verter circuit is a 16 bit delta sigma converter Its internal sample rate is much higher than the output data rate in order to increase accuracy Sampling is controlled by the microprocessor Output data are transferred to the DIGITAL FILTER 4 DIGITAL FILTER The digital filter circuitry is actually software in the ...

Страница 14: ...ons in the PIM 3 7 PROGRAM MEMORY The program memory contains the entire software sequence to be per formed by the microprocessor Storage is 32 768 bytes 8 LIMITS OUTPUTS Open collector outputs are provided for limits and up to four llimits may be set When the signal level exceeds a limit setting the external circuit is completed through the open col lector output See Chapter 12 Understanding Limi...

Страница 15: ...EXCITATION SUPPLY The excitation supply provides a well regulated drive voltage to the trans ducer under control of the microprocessor 11 POWER SUPPLY The power supply uses the input supply 12 to 28 VDC to make voltages and currents for all circuits in the PIM 3 12 ANALOG OUTPUT An optional 0 5 VDC or 4 20mA analog output is available ...

Страница 16: ...3 4 Block Diagram ...

Страница 17: ... or sheet metal screws may also be used Figure 4 1 is a template which may be used for hole location Chassis mounted plastic case A version of the PIM 3 is also available in a plastic case which is designed to be plugged into a multi channel backplane Please note that Figure 4 1 only applies to the metal case not the plastic case 4 2 Wiring Stand alone metal case Four connectors bring signals to a...

Страница 18: ...4 2 Mounting and Wiring ...

Страница 19: ...ctions A SUPPLY is the positive terminal of the power source 12 to 28 VDC B SUPPLY RETURN is the negative terminal of the power source C ANALOG OUTPUT is the negative terminal of the optional analog output D ANALOG OUTPUT is the positive terminal of the optional analog output E DEFAULT pin Suppose for a moment that the address of a PIM 3 has been forgotten or the baud rate is not known Without thi...

Страница 20: ...fault values are shown in Table 4 1 D Auxiliary Connections The Auxiliary Connections contain the four limit output control pins When a limit is on the output terminal is effectively connected shorted to the LIMIT RETURN terminal through a MOSFET transistor The loads con nected to the Limit output pins must be limited to 60 volts DC at 0 5 amperes See Chapter 12 Understanding Limits for an expla n...

Страница 21: ...ho Off Address 00 Full scale Units 20000 mV V 3 Limit 1 Setpoint 10000 Limit 1 Hysteresis 100 Limit 2 Setpoint 500 Limit 2 Hysteresis 100 Limit 3 Hysteresis 100 Limit 4 Setpoint 500 Limit 4 Hysteresis 100 Tare Off Excitation 10V Shunt Cal Units 20000 Continuous Transmit Off Engineerinig Units LBS Auto Limit Report Off ...

Страница 22: ... install another To install another shunt cal resistor proceed as follows 1 Remove mating connectors from PIM 3 and remove the cover of the unit The printed circuit boards will remain attached to the lid 2 Locate the shunt calibration resistor It is located on the ana log circuit board furthest from the lid near the transducer connector location The resistor is mounted in two pin jacks for easy re...

Страница 23: ...Model PIM 3 4 7 ...

Страница 24: ...4 8 Mounting and Wiring ...

Страница 25: ...d into its memory It will not be necessary to ground the DEFAULT pin since proper values or defaults have been loaded into the system when the instrument left the factory There fore proceed as follows 1 Set the communications terminal or computer soft ware being used with the PIM 3 to 9600 baud no parity bits 8 data bits and 1 stop bit 2 Apply power to the PIM 3 3 Select the desired address for th...

Страница 26: ...tablished the baud rate could be changed and other operating parameters set up as desired Remember to alter the baud rate of the terminal or the computer s serial output if you change the PIM 3 s baud rate 6 It is often desired that the PIM 3 be used to auto matically detect the exceeding of a limit Chapter 12 Understanding Limits describes limit setup and opera tion Command F6 will report limit s...

Страница 27: ...6 1 Baud Rate Bits and Parity PIM 3 Instruments always use 8 data bits one start bit and one stop bit and no parity bits often described as N81 for serial communications Baud rates of 300 600 1200 2400 4800 or 9600 baud are available As shipped from the factory PIM 3 Instruments are set to communicate at 9600 baud The baud rate can be changed over the serial communications link using the W1 system...

Страница 28: ...those which affect the opera tion of the transducer amplifier circuit For example if the full scale range of a transducer amplifier is altered an amplifier command is used 6 4 Addressing Every PIM 3 on the communications loop must have a unique two character address As shipped from the fac tory every PIM 3 has an address of 00 ASCII codes decimal 30 decimal 30 A PIM 3 s address can be changed over...

Страница 29: ...communicated with Each character must be a number or an uppercase letter WO is the two character command code to be executed A list of the valid sys tem command codes is given at the beginning of Chapter 10 A list of the valid amplifier command codes are given at the beginning of chapter 11 1 2 is a value in the optional information field needed by commands that write data to the PIM 3 represents ...

Страница 30: ...gnifies if that command is a function command F a read operating parameter command R or a write operating parameter command W Read and write commands can be used to configure the operation of the instrument Function commands are used to gather data from the instrument or to cause it to perform an oper ation All characters received before the pound sign are ignored Therefore one or more PIM 3 instr...

Страница 31: ...id command or when invalid information is given with a write oper ating parameter W command a floating point number as the result of a read operating parameter R or function F command other ASCII strings To signal the end of a response the PIM 3 will send a carriage return ASCII code decimal 13 if the Auto Line feed function is off or a linefeed carriage return ASCII codes decimal 10 decimal 13 wh...

Страница 32: ...6 6 Command Format ...

Страница 33: ...tion Notes The DTE can send the PIM 3 a command string which starts with the character and ends in a Carriage Return If a character is sent without a Carriage Return the PIM 3 will wait 10 seconds for the Carriage Return before resetting its internal communications buffer If the address sent by the DTE matches the address of the PIM 3 and the command string is valid then the PIM 3 will begin proce...

Страница 34: ...used when the DTE has a 9 pin RS 232 serial port The RTS Ready to Send and CTS Clear To Send signals are not used by the PIM 3 Thus they are con nected together in the communications cable in case the DTE such as the IBM PC uses RTS CTS style hardware handshaking Likewise the DTR Data Terminal Ready and DSR Data Set Ready signals are not used by the PIM 3 and are connected together inside the cabl...

Страница 35: ...Model PIM 3 7 3 ...

Страница 36: ...7 4 RS 232 Installation Notes ...

Страница 37: ...IM 3 on the communications bus must have a unique 2 character address Before wiring multiple PIM 3 s into an RS 422 RS 485 communications bus it is rec ommended that you read this document thoroughly and then follow the sequence given below to avoid problems during installation 1 Determine if the bus master has an RS 422 interface or a RS 485 interface Wire up one and only one PIM 3 to the communi...

Страница 38: ...bus master s baud rate not match that of the PIM 3 4 Change this PIM 3 s address to another unique value such as 01 using the W4 Write Instru ment Address command as explained in the Chap ter 6 System Commands Verify communications with the PIM 3 to insure that it is operating with the new address 5 Change this PIM 3 s baud rate to your desired value such as 9600 baud using the W1 Write Baud Rate ...

Страница 39: ...vices It is a full duplex system i e the bus master can transmit and receive data from the slaves at the same time Use the wiring diagram in Figure 8 1 when connecting PIM 3 instruments to a RS 422 bus PIN RS 422 FUNCTION DESCRIPTION 4 Transmit A output Data from the PIM 3 to bus master 5 Transmit B output Data from the PIM 3 to bus master 2 Receive A input Data to the PIM 3 from bus master 3 Rece...

Страница 40: ...ludes a misleading connector pinout The standard designators A and B for positive and negative have been reversed Use the wiring diagram given in Figure 8 2 when connecting PIM 3 Instruments to this card Many other distributors of industrial PC equipment provide PC AT RS 422 RS 485 interface cards and this does not constitute an endorsement by SENSOTEC of Black Box products ...

Страница 41: ...mit and receive data at the same time and that only one device can drive or talk on the bus at a time A PIM 3 Instrument is configured as a two wire RS 485 device when Transmit A pin 4 is connected to Receive A pin 2 and Transmit B pin 5 and Receive B pin 3 are connected together Use the wiring diagram of Fig ure 8 1 for a four wire RS 485 communications bus and use Figure 8 3 when connecting PIM ...

Страница 42: ...without a Carriage Return the PIM 3 will wait 10 seconds for the Carriage Return before resetting its internal communications buffer If the address sent by the DTE matches the address of the PIM 3 and the command string is valid then the PIM 3 starts processing the command string After the PIM 3 has finished processing the command string the PIM 3 will send a response if neccessary ...

Страница 43: ... that are received on the screen Another BASIC program is provided which dem onstrates how data can be read from a PIM 3 as often as possible by using the PIM 3 s Continuous Transmit func tion Also included are hints for communicating with a PIM 3 using Procomm Plus or the Microsoft Windows 3 1 Ter minal 9 2 Sample QBasic Programs Below are sample terminal programs for Microsoft QBasic or QuickBas...

Страница 44: ...uickBasic program to REM communicate to Sensotec Model PIM 3 PRINT PRINT PIM3TERM Sample QBasic program for Sensotec PIM 3 PRINT REM The CS0 turns off the checking of CTS handshaking REM The DS0 turns off the checking of DSR handshaking OPEN COM1 9600 N 8 1 CS0 DS0 TB2048 RB2048 FOR RANDOM AS 1 PRINT Press ESC to exit DO WHILE done 0 IF LOC 1 0 THEN in INPUT 1 1 PRINT in out INKEY IF LEN out 0 THE...

Страница 45: ... CHR 27 THEN done 1 LOOP CLOSE 1 PRINT PIMCTRAN done END Listing 2 Sample QBasic Program for PIM 3 Continuous Transmit 9 3 Hints for Procomm Plus for DOS Since PIM 3 series instruments do not use either RTS CTS or XON XOFF handshaking you must change the standard Procomm Plus for DOS setup To do this enter the Procomm Plus Setup Utility by press ing ALT S then select Terminal Options Change both t...

Страница 46: ...9 4 Application Programs Figure 9 1 Windows 3 1 Terminal Communications Settings ...

Страница 47: ...d Parameter W1 Serial communications baud rate Yes W2 Serial communications Automatic linefeed Yes W3 Serial communications Echo W4 Serial communications address WA RA Limit 1 setpoint value Yes WB RB Limit 1 hysteresis value Yes WC RC Limit 2 setpoint value Yes WD RD Limit 2 hysteresis value Yes WE RE Limit 3 setpoint value Yes WF RF Limit 3 hysteresis value Yes WG RG Limit 4 setpoint value Yes W...

Страница 48: ...he four open collector limits A limit status message looks something like this AA L1 ON L2 ON L3 OFF L4 OFF Where AA is the address of the PIM 3 EXAMPLE 00F6 The above command when followed by a carriage return will cause the instrument addressed as 00 to transmit its limit status WHEN TO USE IT Use this command whenever you wish to know the status of the limits ...

Страница 49: ...iven the PIM 3 will respond with COMMAND ERROR To temporarily reset the baud rate to 300 baud use the DEFAULT pin as described in Chapter 4 Mounting and Wiring EXAMPLE 00W10 The above command when followed by a carriage return will cause the instrument addressed as 00 to use a baud rate of 9600 for all subsequent serial communications This command is a universal command Sending this command for th...

Страница 50: ...inefeed function is turned off and messages from the instrument end with a carriage return This is the default setting when the instrument is shipped from the factory The PIM 3 will not send a response after this command has been processed To temporarily set the automatic linefeed setting to on use the DEFAULT pin as described in Chapter 4 Mounting and Wiring EXAMPLE 00W21 The above command when f...

Страница 51: ...3 will not send a response after this command has been processed If incorrect information is given the PIM 3 will respond with COMMAND ERROR To temporarily set the echo setting to off use the DEFAULT pin as described in Chapter 4 Mounting and Wiring EXAMPLE 00W31 The above command when followed by a carriage return will turn on the echo for the instrument addressed as 00 WHEN TO USE IT If the PIM ...

Страница 52: ... are shipped from the fac tory is 00 ASCII codes decimal 30 decimal 30 The PIM 3 will not send a response after this command has been processed To temporarily set the address to 00 use the DEFAULT pin as described in Chapter 4 Mounting and Wiring EXAMPLE 00W4AA The above command when followed by a carriage return will change the two character address of the instrument addressed as 00 to AA WHEN TO...

Страница 53: ...alue in the engineering units The hysteresis for each limit may be changed with the WB WD WF WH com mand For a complete explanation of limit parameters please see Chapter 12 Understanding Limits The PIM 3 will not send a response after this command has been processed If incorrect information is given the PIM 3 will respond with COMMAND ERROR The RA RC RE and RG commands are used to read limit setp...

Страница 54: ...in the information field are the value in the engineering units The setpoint for each limit may be changed with the WA WC WE and WG commands For a complete explanation of limit parameters please see Chapter 12 Understanding Limits The PIM 3 will not send a response after this command has been processed If incorrect information is given the PIM 3 will respond with COMMAND ERROR The RB RD RF and RH ...

Страница 55: ...uto matically transmit the limit status whenever any one of the limits has been switched from off to on A sample limit status message looks like this AA L1 ON L2 OFF L3 OFF L4 OFF Where AA is the address of the PIM 3 EXAMPLE 00WJ1 The above command when followed by a carriage return will cause the instrument addressed as 00 to enable its automatic limit reporting function WHEN TO USE IT The automa...

Страница 56: ...system command F0 repeatedly The PIM 3 will still respond to other com mands normally The PIM 3 will not send a response after this command has been processed If incorrect information is given the PIM 3 will respond with COMMAND ERROR EXAMPLE 00WI1 The above command when followed by a carriage return will cause the instrument addressed as 00 to transmit data as quickly as possible one reading afte...

Страница 57: ...on SYNOPSIS RR Read software revision level DESCRIPTION The RR command reads the instrument s software part number and software revision level EXAMPLE The command 00RR when followed by a carriage return produces a response similar to 084 1003 00 2 4 ...

Страница 58: ...10 12 System Commands ...

Страница 59: ... Transmit data F1 Activate Tare Yes F2 Clear Tare Yes F3 Calibrate Analog to Digital Converter Yes F4 Calibrate Amp using Shunt Cal method Yes F5 Apply Shunt Resistor and Transmit Reading F7 Transmit Average Value F8 Calibrate Amp using Known Load method Yes Write Command Read Command Parameter W5 R5 Full Scale Value Yes W6 R6 Engineering Units Yes W7 R7 Full Scale millivolt Volt W8 R8 Shunt Calib...

Страница 60: ...nuously reading the transducer and this function transmits the latest data point computed If the transducer signal is beyond the capability of the PIM 3 to measure the PIM 3 will respond with OVER for overrange and UNDER for underrange EXAMPLE 00F0 The above command when followed by a carriage return will cause the instrument addressed as 00 to transmit the data For example 5670 5 LBS ...

Страница 61: ...n send the F2 command The PIM 3 will not send a response after this command has been processed This command is a universal command Sending this command for the spe cial address of FF will cause all PIM 3 s on the communications link to pro cess the command EXAMPLE 00F1 The above command when followed by a carriage return will cause the instrument addressed as 00 to activate the Tare Zero function ...

Страница 62: ...tion you can send the F1 command The PIM 3 will not send a response after this command has been processed This command is a universal command Sending this command for the spe cial address of FF will cause all PIM 3 s on the communications link to pro cess the command EXAMPLE 00F2 The above command when followed by a carriage return will cause the instrument addressed as 00 to clear the Tare Zero o...

Страница 63: ... calibrated when the PIM 3 instrument is pow ered up This command is a universal command Sending this command for the spe cial address of FF will cause all PIM 3 s on the communications link to pro cess the command EXAMPLE 00F3 The above command when followed by a carriage return will cause the instrument addressed as 00 to tell the analog to digital converter chip to perform a calibration WHEN TO...

Страница 64: ...r s calibration record such as excitation voltage full scale mV V value shunt cal value etc should be entered into the PIM 3 before calibrating Also the unit should be tared zeroed with the F1 command before calibrating span with the F4 command See Chapter 13 Calibration Examples for a detailed example of calibrating a PIM 3 to a transducer using the Shunt Calibration method EXAMPLE 00F4 The above...

Страница 65: ...ucers on the amplifier channel to two transducer leads usually SIG and SENSE for SENSOTEC transducers and transmits the reading EXAMPLE 00F5 The above command when followed by a carriage return will cause the instrument addressed as 00 to apply the shunt resistor to the transducer and transmit the reading WHEN TO USE IT This can be used as quick check to verify that a strain gauge transducer is co...

Страница 66: ... incre ments an average counter The next time the F7 command is used the average value is transmitted and both the average total and average value are reset The PIM 3 then continues gathering data into the average total and counter The PIM 3 will gather average values for up to 35 minutes between instances of the F7 command after which the average total and counter are reset automatically EXAMPLE ...

Страница 67: ...oad value etc should be entered into the PIM 3 prior to calilbrating Also the unit should be tared zeroed with the F1 command before calibrating span with the F8 command See Chapter 13 Calibration Examples for a detailed example of calibrating a PIM 3 to a transducer using the Known Load Method EXAMPLE 00F8 The above command when followed by a carriage return will cause the instrument addressed as...

Страница 68: ...been processed If incorrect information is given the PIM 3 will respond with COMMAND ERROR This command is a universal command Sending this command for the spe cial address of FF will cause all PIM 3 s on the communications link to pro cess the command EXAMPLE The command below when followed by a carriage return will change the full scale value to 30 75 with 2 decimal places 00W530 75 WHEN TO USE ...

Страница 69: ...d a response after this command has been processed If incorrect information is given the PIM 3 will respond with COMMAND ERROR This command is a universal command Sending this command for the spe cial address of FF will cause all PIM 3 s on the communications link to pro cess the command EXAMPLE The command below when followed by a carriage return will change the text that is transmitted to CATS 0...

Страница 70: ...tion factor The PIM 3 will not send a response after this command has been processed If incorrect information is given the PIM 3 will respond with COMMAND ERROR EXAMPLE The command below when followed by a carriage return will change the mV V value to 3 75 mV V 00W73 75 WHEN TO USE IT The full scale millivolt volt value is set if the instrument was purchased with a SENSOTEC transducer This command...

Страница 71: ...r is scaled to this value The PIM 3 will not send a response after this command has been processed If incorrect information is given the PIM 3 will respond with COMMAND ERROR This command is a universal command Sending this command for the spe cial address of FF will cause all PIM 3 s on the communications link to pro cess the command EXAMPLE The command below when followed by a carriage return wi...

Страница 72: ...ge is set to 10 volts DC The PIM 3 will not send a response after this command has been processed The R9 command will read the present excitation voltage This command is a universal command Sending this command for the spe cial address of FF will cause all PIM 3 s on the communications link to pro cess the command EXAMPLE 00W91 The above command when followed by a carriage return will change the s...

Страница 73: ...transducer using the Known Load this is the value that should be applied to the transducer during calibration The PIM 3 will acknowledge the write command by responding with OK The RK command is used to read the known load calibration value EXAMPLE The command below when followed by a carriage return will change the known load calibration value to 20000 00WK20000 WHEN TO USE IT The known load cali...

Страница 74: ...11 16 Amplifier Commands ...

Страница 75: ...does not exceed a pre established refer ence value FAIL SAFE A configuration of limits such that normal operation never produces the same condition produced by power failure LOW LIMIT A limit configuration in which the limit is tripped when the signal is less than the limit reference setting HIGH LIMIT A limit configuration in which the limit is tripped when the signal is more than the limit refer...

Страница 76: ...lways lies between the trip point and zero Thus a limit setting of 5000 with a hys teresis value of 100 would energize the limit at 5000 and deenergize it at 4900 Such a hystere sis value would be considered as negative i e 100 See Figure 12 1 2 High limits always have negative hysteresis Low limits always have positive hysteresis ...

Страница 77: ...Model PIM 3 12 3 ...

Страница 78: ...p if the signal falls below the setpoint so a low limit will work for the lower limit 2000 pounds Suppose that it is decided that noise does not exceed 1 of the full scale value or 0 01 x 10000 100 pounds Since rule 2 must apply the high limit hysteresis is a 100 pounds and the low limit hysteresis is 100 pounds Either limit may be designated as either value since the sign of the hysteresis will t...

Страница 79: ...Model PIM 3 12 5 ...

Страница 80: ... could overflow Because of slopping around of the tank liquid a 2 noise limit 0 02 x 3000 150 gallons is safe First the 2900 gallon point is considered to be a dan ger point and we want a limit to be fired if that level is exceeded That means that the upper upper limit is a high limit We will call it Limit 1 Since it is a high limit the hysteresis is negative Limit 1 Setpoint 2900 Limit 1 Hysteres...

Страница 81: ...gh low limits but we could drive the relay nor mally and use the normally closed contacts of the relay to drive the pump Putting the two limits outputs in parallel as drivers to the relay would accomplish this The 2500 gallon limit becomes a high limit hysteresis is negative and the 500 gallon limit becomes a low limit hysteresis is positive Limit 2 Setpoint 2500 Limit 2 Hysteresis 150 Limit 3 Set...

Страница 82: ...LIMIT 3 SETPOINT LIMIT 3 HYSTERESIS LIMIT 2 HYSTERESIS LIMIT 2 SETPOINT LIMIT 1 SETPOINT LIMIT 1 HYSTERESIS 1 K 2 K 3 K 0 OFF ON OFF SHUTOFF DANGER POINT Figure 12 3 Limit Example 2 Setup A B C D E F SHUTDOWN SYSTEM HORN PUMP POWER SUPPLY K 1 Figure 12 4 Limit Example 2 Circuit ...

Страница 83: ... a transducer Model PIM 3 Digital Inline Amplifier 12 28 volt DC power supply to power the PIM 3 Communications terminal or a personal computer running a terminal emulation program Transducer to which the PIM 3 is to be calibrated The full scale millivolt per volt mV V calibra tion factor value and the excitation voltage for the transducer must be known A means of removing all load from the transd...

Страница 84: ...age return ASCII code 13 decimal shown here as ret 01W5150 ret 01W6pounds ret 01W72 997 ret 01WK100 ret 01W91 ret Second the analog to digital converter inside the PIM 3 is internally calibrated to minimize temperature errors This may be done regardless of the load on the trans ducer 01F3 ret Next the tare value will be entered into the PIM 3 All load must be removed from the transducer before thi...

Страница 85: ...d for proper shunt calibration of a Model PIM 3 to a trans ducer Model PIM 3 Digital Inline Amplifier 12 28 volt DC power supply to power the PIM 3 Communications terminal or a personal computer running a terminal emulation program Transducer to which the PIM 3 is to be calibrated The full scale millivolt per volt mV V calibra tion factor value the excitation voltage and the shunt calibration valu...

Страница 86: ...y set to 01 with the W4 command Usually PIM 3 s are shipped with a 59 00K ohm preci sion shunt calibration resistor installed for calibrating transducers with the shunt calibration method If the transducer used with the PIM 3 requires a different resis tor value it may be necessary to remove the 59 00K ohm resistor and install another Please examine the Chapter 4 Mounting and Wiring for informatio...

Страница 87: ...gardless of the load on the trans ducer 01F3 ret Next the tare value will be entered into the PIM 3 All load must be removed from the transducer before this command is performed so that the PIM 3 will recognize this point as zero 01F1 ret Then calibrate the system using the shunt cal value Make certain that there is still no load being applied to the transducer 01F4 ret This completes the system s...

Страница 88: ...mand to apply the shunt calibration resistor to the transducer and take a reading When no load is applied to the trans ducer this reading allows you to check the actual shunt calibration reading against the calculated shunt calibration reading entered with the W8 command ...

Страница 89: ...For example a single 500 pound load cell could have two PIM 3 s connected to it One instrument could be set up with its full scale as 500 pounds and the second could be set up with its full scale at 100 pounds When the load is less than 100 pounds the second instrument s output would offer greater resolution than the first instrument s output If this load cell s output is 5 000mV V at full scale t...

Страница 90: ...l usage Replacement or repaired product will be shipped F O B our plant The terms of this war ranty do not extend to any product or part thereof which under normal usage has an inherently shorter useful life than one year The replacement warranty detailed here is the buyer s exclusive remedy and will satisfy all obligations of SENSO TEC whether based on contract negligence or otherwise SENSOTEC is...

Страница 91: ... SENSOTEC shall be at buyer s expense and repaired or replacement items will be shipped F O B our plant in Columbus Ohio Non verified problems or defects may be subject to an evalua tion charge Please return the original calibration data with the unit Obtaining Non Warranty Service Advance authorization is required prior to the return to SENSOTEC Before returning the item either write to the Custo...

Страница 92: ...ase return the original calibration data with the unit Repair Warranty All repairs of SENSOTEC products are warranted for a period of 90 days from date of shipment This warranty applies only to those items which are found defective and repaired and does not apply to products in which no defect was found and returned as is or merely recalibrated Out of war ranty products may not be capable of being...

Страница 93: ...Amplifier using the Shunt Cali bration Value entered with the W8 Com mand The transducer must not be loaded at this time Yes F5 Check Shunt Calibration Applies shunt calibration resistor to the transducer allows time to stabillize then transmits the reading F6 Request Limit Status F7 Request Average Value since last F7 Command Average is updated each 32 77 milliseconds Maximum time before auto res...

Страница 94: ...e R9 Reads Excitation 5V 0 10V 1 RA Read Limit 1 Setpoint RB Read Limit 1 Hysteresis Setting RC Read Limit 2 Setpoint RD Read Limit 2 Hysteresis Setting RE Read Limit 3 Setpoint RF Read Limit 3 Hysteresis RG Read Limit 4 Setpoint RH Read Limit 4 Hysteresis RJ Read Limit Automatic Limit Report Status RK Reads Known Load Calibration Value RR Reads Internal Revision Level of Software ...

Страница 95: ... 3 decimals maximum XXXX XXX XXXXXXX Yes W6 Set Engineering Units 10 character maxi mum Yes W7 Set Full scale mV V 1 to 5 mV V with 10 volts excitation 5 to 10 mV V W8 Set Shunt Calibration Value Yes W9 Set Excitation Voltage 0 5V 1 10V Yes WA Set Limit 1 Setpoint 0 to Full scale in engineering units for all setpoints Yes WB Set Limit 1 Hysteresis 0 to 100 for all setpoints Yes WC Set Limit 2 Setp...

Страница 96: ...ff for RS 485 with multiple units WK Set Known Load Calibration Value Yes SPECIAL COMMAND CODE FUNCTION ZZ Initiates interactive command structure to set zero and span of analog output either 4 20 mA or 0 5 volts This command also has in house testing features not normally required by the customer WRITE COMMAND LISTING CODE FUNCTION UNIVERSAL COMMAND ...

Страница 97: ...A 8 Appendix ...

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