background image

OM-USB-5203 User's Guide  

Sensor Connections 

11 

Thermocouple connections 

Connect thermocouples to the OM-USB-5203 such that they are floating with respect to GND. A thermocouple 
consists of two dissimilar metals that are joined together at one end. When the junction of the metals is heated 
or cooled, a voltage is produced that correlates to temperature. 

The OM-USB-5203 makes fully-differential thermocouple measurements without the need of ground-
referencing resistors. A 32-bit floating point value in either a voltage or temperature format is returned by 
software. An open thermocouple detection feature is available for each analog input which automatically detects 
an open or broken thermocouple.  

Use InstaCal to select the thermocouple type (J, K, R, S, T, N, E, and B) and one or more sensor input channels 
to connect the thermocouple. 

Wiring configuration 

Connect the thermocouple to the OM-USB-5203 using a differential configuration, as shown in Figure 3. 

 

Figure 3. Typical thermocouple connection 

Connect thermocouples to the OM-USB-5203 such that they are floating with respect to GND. The OM-USB-
5203ground pins are isolated from earth ground, so you can connect thermocouple sensors to voltages 
referenced to earth ground as long as the isolation between the GND pins and earth ground is maintained. 

When thermocouples are attached to conductive surfaces, the voltage differential between multiple 
thermocouples must remain within ±1.4 V. For best results, use insulated or ungrounded thermocouples when 
possible. 

Maximum input voltage between analog input and ground 

The absolute maximum input voltage between an analog input and the isolated GND pins is ±24 VDC when the 
OM-USB-5203 is powered on or off. 

If you need to increase the length of your thermocouple, use the same type of thermocouple wires to minimize 
the error introduced by thermal EMFs. 

RTD and thermistor connections 

A resistance temperature detector (RTD) measures temperature by correlating the resistance of the RTD 
element with temperature. A thermistor is a thermally-sensitive resistor that is similar to an RTD in that its 
resistance changes with temperature – thermistors show a large change in resistance that is proportional to a 
small change in temperature. The main difference between RTD and thermistor measurements is the method 
used to linearize the sensor data. 

RTDs and thermistors are resistive devices that require an excitation current to produce a voltage drop that can 
be measured differentially across the sensor. The device has four built-in current excitation sources (±I1 to ±I4) 
for measuring resistive type sensors. Each current excitation terminal is dedicated to one channel pair. 

The OM-USB-5203 makes two, three, and four-wire measurements of RTDs (100 

Ω platinum type) and 

thermistors.  

Содержание OM-USB-5203

Страница 1: ...omega com e mail info omega com Forlatestproductmanuals omegamanual info IS09001 IS09001 CEIITIRED CEIITIFIB CORPOMlEQIJMJlY CDRPORAJEQUAlJTY STAMFORD CT MANCHESTl R UK OM USB 5203 8 Channel Temperatu...

Страница 2: ...6 USA Canada only Tel 203 359 1660 Fax 203 359 7700 e mail info omega com For Other Locations Visit omega com worldwide omega com info omega com The information contained in this document is believed...

Страница 3: ...itation output terminals I1 to I4 10 Four wire two sensor common terminals 4W01 to 4W67 10 Two sensor common terminals IC01 to IC67 10 Digital terminals DIO0 to DIO7 10 Power output terminals 5V 10 Gr...

Страница 4: ...Specifications 21 Analog input 21 Channel configurations 21 Compatible sensors 22 Accuracy 22 Thermocouple measurement accuracy 22 Semiconductor sensor measurement accuracy 23 RTD measurement accuracy...

Страница 5: ...ts present information to help you avoid injuring yourself and others damaging your hardware or losing your data bold text Bold text is used for the names of objects on a screen such as buttons text b...

Страница 6: ...d microprocessor automatically linearizes the measurement data according to the sensor category The OM USB 5203 features eight independent temperature alarms Each alarm controls an associated digital...

Страница 7: ...and time Data is stored on the memory card in binary files After logging measurements you can transfer the files to your computer You can use InstaCal to convert the files to csv format for use in Mi...

Страница 8: ...red A green Status LED turns on when power is applied When you connect the device for the first time a Found New Hardware dialog opens when the operating system detects the device The dialog closes af...

Страница 9: ...e bottom edge Each row has 26 connections Between each bank of screw terminals are two integrated CJC sensors used for thermocouple measurements Signals are identified in Figure 2 Figure 2 OM USB 5203...

Страница 10: ...channel 2 and channel 3 I3 is the current excitation source for channel 4 and channel 5 I4 is the current excitation source for channel 6 and channel 7 Four wire two sensor common terminals 4W01 to 4W...

Страница 11: ...und is maintained When thermocouples are attached to conductive surfaces the voltage differential between multiple thermocouples must remain within 1 4 V For best results use insulated or ungrounded t...

Страница 12: ...ons to the sensor With this method the two wires that provide the RTD sensor with its excitation current also measure the voltage across the sensor Since RTDs exhibit a low nominal resistance measurem...

Страница 13: ...ensation For accurate three wire compensation the individual lead resistances connected to the I pins must be of equal resistance value Four wire configuration With a four wire configuration connect t...

Страница 14: ...semiconductor sensor is small when compared to thermocouples and RTDs However semiconductor sensors can be accurate inexpensive and easy to interface with other electronics for display and control The...

Страница 15: ...igital I O and conductive thermocouples the thermocouples are no longer isolated In this case thermocouples must not be connected to any conductive surfaces that may be referenced to earth ground For...

Страница 16: ...ware algorithm automatically corrects for the additional thermocouples created at the terminal blocks by subtracting the calculated cold junction voltage from the analog input s thermocouple voltage m...

Страница 17: ...age by the current excitation level Ix source The value of the Ix source is stored in local memory Once the resistance value is calculated the value is linearized in order to convert it to a temperatu...

Страница 18: ...b Blinks continuously Data is being transferred Upon connection the LED blinks a few times and then remain on indicates a successful installation Blinks several times Initial communication is establis...

Страница 19: ...JC enabled 512 000 000 1 1 1 6 4 8 512 000 000 1 8 1 6 4 8 Data logging button Use the data logging button to end a data logging session The data logging button is also used to start recording data wh...

Страница 20: ...the files to your computer by reconnecting the OM USB 5203 to a USB port on your computer or by removing the CompactFlash card from the OM USB 5203 and using a card reader connected to your computer...

Страница 21: ...bits No missing codes 24 bits Input coupling DC Warm up time 30 minutes min Open thermocouple detect Automatically enabled when the channel pair is configured for thermocouple sensor The maximum open...

Страница 22: ...RTD 100 PT DIN 43760 0 00385 ohms ohm C 100 PT SAMA 0 003911 ohms ohm C 100 PT ITS 90 IEC751 0 0038505 ohms ohm C Thermistor Standard 2 252 through 30 000 Semiconductor IC LM35 TMP35 or equivalent Acc...

Страница 23: ...Accuracy Error C LM35 TMP35 or equivalent 40 to 150 0 50 RTD measurement accuracy The error shown in Table 6 below does not include errors of the sensor itself The sensor linearization is performed u...

Страница 24: ...0 05 5000 35 to120 0 05 10000 25 to120 0 05 30000 10 to120 0 05 Typical resistance values at various temperatures for supported thermistors are shown in Table 8 below The device cannot measure resist...

Страница 25: ...ter Specification Digital type CMOS Number of I O 8 DIO0 through DIO7 Configuration Independently configured for input or output Power on reset is input mode unless bit is configured for alarm Pull up...

Страница 26: ...1 Alarm when input temperature T1 reset alarm when input temperature goes below T2 Alarm when input temperature T1 Alarm when input temperature T1 reset alarm when input temperature goes above T2 Alar...

Страница 27: ...p methods Stop on button press To stop logging press and hold the button until the LED turns off The device caches logged data in volatile memory prior to writing to memory card When logging always us...

Страница 28: ...e device which includes up to 10 mA for the status LED Note 4 Self powered hub refers to a USB hub with an external power supply Self powered hubs allow a connected USB device to draw up to 500 mA Thi...

Страница 29: ...Specification Configuration 4 dedicated pairs Current excitation output AI channel I1 I1 CH0 CH1 I2 I2 CH2 CH3 I3 I3 CH4 CH5 I4 I4 CH6 CH7 Current excitation output ranges Thermistor 10 A typ RTD 210...

Страница 30: ...d 35 NC No connection 10 I1 CH0 CH1 current excitation return 36 I4 CH6 CH7 current excitation source CJC sensor CJC sensor 11 I2 CH2 CH3 current excitation source 37 I3 CH4 CH5 current excitation ret...

Страница 31: ...y OMEGA if the unit is found to be defective it will be repaired or replaced at no charge OMEGA s WARRANTY does not apply to defects resulting from any action of the purchaser including but not limite...

Страница 32: ...ity Indicators Turbine Paddlewheel Systems Totalizers Batch Controllers pH CONDUCTIVITY pH Electrodes Testers Accessories Benchtop Laboratory Meters Controllers Calibrators Simulators Pumps Industrial...

Отзывы: