Amptec Research 720A Operation And Maintenance Manual Download Page 27

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720A Operation and Maintenance Manual – Rev S – January 25, 2019

Page 27

13231 Rooster Springs Rd.,

Austin, TX 78737

(512) 858-4045

[email protected]

amptec.com

Trim pot at RV1:

Influences full-scale on all ranges.

Trim pot at RV2:

Influences zero-scale on all ranges.

Trim pot at RV5:

Influences zero-scale on 200 m

Ω

range.

Trim pot at RV6:

Influences full-scale on 200 m

Ω

range.

All other trim pots on the board, including RV3 and RV201 shown in

Figure 9

, are not

used during standard product recalibration and should not be adjusted during this

procedure.

E-4.3 Calibration Procedure Adjustments

This section contains information on the specific adjustments necessary to calibrate a

720A meter. Ensure that you have first followed the instructions detailed in the

calibration procedure overview in section X before completing any of the internal

adjustments below. It is recommended that you complete the following steps in order.

1. Zero Adjustment:

Select the 200

Ω

range. Connect the meter via the

measurement test leads across a precision 1.0

resistance standard with ± 0.005% or better accuracy.

Adjust the trim-pot (RV2) to make the meter read 1.00

(100 counts on the display). Note that this process

will be repeated on the 200

mΩ

range with a 0.001

Ω

standard

after

the full-scale adjustment is performed.

2. Full-Scale Adjustment:

Connect the meter via the measurement test leads

across a precision 100

resistance standard with ±

0.005% or better accuracy. Adjust the full-scale pot

(RV1) to make the meter read 100.00

(10000

counts on the display).

3. 200 m

Adjustment:

Next, the 200 m

range needs to be calibrated. The

trim pots adjusted above (RV1 & RV2) affect every

range of the meter, while RV5 & RV6 only affect the

200 m

range. Therefore, they must be adjusted last.

4. 200 m

Zero Adjustment:

Select the 200 m

range. Connect the meter

via the measurement test leads across a precision

0.001

resistance standard with ± 0.01% or better

accuracy. Adjust the trim-pot (RV5) to make the meter

read 01.00 mΩ (100 counts on the display).

5. 200 m

Full-Scale Adjustment:

Connect the meter via the measurement test leads

across a precision 100 m

resistance standard with ±

0.005% or better accuracy. Adjust the full-scale pot

(RV6) to make the meter read 100.00 m

(10000

counts on the display).

Summary of Contents for 720A

Page 1: ...13231 Rooster Springs Rd Austin TX 78737 T 512 858 4045 E info amptec com amptec com AMPTEC RESEARCH MODEL 720A OPERATION AND MAINTENANCE MANUAL ...

Page 2: ...Jack Terminals p 12 D 2 5 Autorange Button and Function Information p 12 D 2 6 Unit of Measurement LEDs p 12 D 3 Rear Panel Features p 13 D 3 1 Fuse Holder and Fuse Information p 13 D 3 2 AC Inlet p 14 D 3 3 RS 232C Terminal Block p 14 D 3 4 RS 232C Connector p 14 D 3 5 Fan Fan Guard and Air Intake p 15 D 3 6 DC Power Jack p 15 D 4 Battery Holder Design and Description p 15 D 5 Test Lead Connectio...

Page 3: ...ting bolted joint resistance of cable connections and earth ground testing Component testing matching and sorting resistors all types pots strain gouges shunts I C substrates thick film circuits small motors and small transformers chokes thermistors fuses extruded copper wire Nichrome wire all alloys of wire healing elements printed circuit board clad resistance plated through holes and plating th...

Page 4: ...allow up to thirty 30 minutes of warm up instead a Optional Perform a zero check for test lead probe integrity i Connect a set of leads probes to the front panel via the VHI and VLO banana jack terminals on the unit s front panel ii Short the leads probes by touching the ends i e alligator clips spear tips etc of each cable to each other iii Select the 200 Ω range on the unit s front panel iv Read...

Page 5: ...isplay flashes zeros Storage Temperature 20 C to 70 C Temperature Coefficient 0 1 x accuracy per degree C Temperature Range Operating temperature 0 C to 50 C at rated accuracy above Storage temperature 20 C to 70 C Terminal Configuration 4 wire Kelvin banana jack binding posts Weight 4 lbs B 2 Specifications for AC Input The AC Input power option for the 720A allows the user to plug the meter dire...

Page 6: ...he meter is fully charged It is safe to leave the charger plugged in even on a full charge as the charger will adjust the output current on a full charge and not damage the batteries Batteries 8 D Cell NiMH nominal capacity is 5000mAh nominal voltage is 1 2V Battery Charger AMPTEC 720 DC smart charger Battery Charger Charging Current 800mA typical with 1A peak Battery Charger Input Voltage 90 VAC ...

Page 7: ...ive the most current list of 720A compatible options 720A Product Packages 720A COMMERCIAL 720A meter lead pouch OP 110 clip leads OP 300 and mini probes OP 403 720A NSN 720A meter RS 232C interface OP 232 autorange feature lead pouch OP 110 clip leads OP 300 and mini probes OP 403 720A Meter Accessories OP 100 Hard shell case for meter OP 110 Test lead storage pouch 720 AC AC power cord for the 7...

Page 8: ...A Digital Micro Ohmmeter Transit case has custom die cut foam insert that allows the unit to fit snugly allowing for minimal movement or damage to occur while transporting Item B AC power supply or battery charger depending upon product version Transit case has custom die cut foam insert that allows power supply to fit snugly Item C Two lead probe sets may vary from photo Transit case has custom d...

Page 9: ...w AUTO and the unit will automatically select the appropriate range when it takes a measurement Next place the measurement leads probes across the unknown resistance value that needs to be measured At this point the 720A meter should start updating the LED display once an electrical connection has been made If your 720A is using the autorange feature one of the three LEDs to the right of the displ...

Page 10: ...and a power outlet If equipped with the 720 BAT option this issue may indicate dead batteries which can be resolved by charging the unit s batteries with the power supply provided by AMPTEC If you have continued difficulty troubleshooting a unit that won t operate when turned on contact AMPTEC for assistance D 2 2 Range Switches These switches refer to item 2 within Figure 2 control which range th...

Page 11: ... above Figure 3 demonstrates the low battery indicator on the unit s front panel Whenever the unit s batteries are nearly depleted having only 4V or less of remaining power the unit will indicate this with a dash appearing on the leftmost LED of the display Once the unit s low battery indicator is triggered the unit has approximately 30 minutes of usage left before the batteries will be entirely d...

Page 12: ...eter Pressing this button enables the unit to automatically select its range of measurement thus activating the unit s autorange mode To use this button feature first ensure that all other range buttons are fully extended deselected and press the AUTO button If you would like to disable this feature and manually select your range of measurement you may simply press the appropriate range switch and...

Page 13: ...ram highlights which feature will be described further in this section Please note that the appearance and layout of your unit s rear panel may vary from these diagrams slightly depending upon the options that your unit is outfitted with and its year of manufacture D 3 1 Fuse Holder and Fuse Information This cap refer to item 1 within Figure 4 holds the unit s 2A fuse in place The unit will accept...

Page 14: ... resistances readings to be taken from the rear of the meter Each gold terminal is electrically connected to the front panel post of the same label To take a reading from the rear panel connect the measurement leads to each pin of the rear terminal block using the rear terminal screws shown in Figure 6 Clip or ring tongue termination ends fasten securely to the screws Connect the opposite ends of ...

Page 15: ... s batteries with any charger not supplied by AMPTEC If operating this unit from outside of the U S please contact AMPTEC for assistance in purchasing a different variation of charger or an outlet adaptor D 4 Battery Holder Design and Description The battery powered version of the 720A Digital Micro Ohmmeter has two battery holders inside which are affixed to the bottom plate of the unit Each batt...

Page 16: ...ontact resistance Figure 7 below and the rest of this section provide a detailed description of how this is achieved Figure 7 illustrates the 4 wire Kelvin principle which eliminates lead wire length and test lead connection contact resistances as potential sources of measurement errors The internal constant current source inherently overcomes all in series resistance within voltage compliance lim...

Page 17: ...ward on the unit s front panel The unit s display should engage immediately One should allow the unit at least fifteen 15 minutes of time to warm up before attempting to make measurements If operating a 720A meter in a more extreme climate a warm up period of thirty 30 minutes is ideal This warm up period allows the unit to adjust to the room s ambient temperature and enables it to accurately take...

Page 18: ...hat is a non conductor Press and hold each probe with a steady hand one on the part under test and one on the metal chassis and do not move the probes for 3 to 5 seconds If using the autorange function the meter needs a little settling time to automatically determine which range is best before displaying a resistance value If your 720A meter does not have an autorange function and the resistance v...

Page 19: ...d correctly send a V command to read the firmware version back from the meter Additional commands are listed in the following section D 7 1 Note Readings taken through the RS 232C communication interface may be from either the front or rear panel D 7 1 RS 232C Commands and Data Format This section details the commands necessary to communicate with your 720A meter via its RS 232C connection The RS ...

Page 20: ...0 KΩ range r7 Selects the 200 KΩ range Data Format The RS 232C Interface outputs reading data in the following format 1 2345E 4 The measurement is always in ohms and the number following E is the exponent multiplier For example 1 2345E 4 is equal to 12 345 KΩ Range Exponent 200 mΩ E 1 2 Ω E 0 20 Ω E 1 200 Ω E 2 2 KΩ E 3 20 KΩ E 4 200 KΩ E 5 Please note that an overrange reading will be indicated b...

Page 21: ...past 20 years Part of this support is offering maintenance repair and calibration services for our instrumentation Our staff is highly trained across all our product lines and is capable of fixing nearly any issue your instrument may have AMPTEC maintains one sole facility for both the manufacturing and repair of its products AMPTEC RESEARCH CORP 13231 Rooster Springs Rd Austin TX USA 78737 Should...

Page 22: ...charge the batteries power the unit is in proper working order If your outlet has a reset button try pressing it and see if the unit will then respond C Check that the external fuse on the rear panel is still intact Unscrew the fuse holder on the unit s rear panel and visually inspect the fuse inside A blown fuse will need to be replaced but can be done so by the end user with any compatible 3AG 2...

Page 23: ...ge temperatures for your unit Any deviations from these temperature specifications will require the end user to at a minimum apply the necessary temperature coefficients to the unit s readings and allow longer warm up times for the product B Ensure that you are allowing enough time for the unit to adjust to ambient temperature before taking readings Under normal circumstances the unit should be gi...

Page 24: ... display should read 100 00 mΩ 10 counts depending on the resistor s accuracy If the above test proves untrue then the DVM circuitry is possibly faulty and may need replacing See section E 2 for more information about sending your product in for repair E 4 720A Calibration Procedure Overview This section of the manual contains information regarding calibration of the AMPTEC 720A Digital Micro Ohmm...

Page 25: ...ance standard Using a trimmer potentiometer also referred to as trim pots adjustment tool you will then rotate the small screw like component affixed to the top of each trim pot that corresponds to each range see Figure 10 Once the unit displays the desired reading you have finished adjusting that particular range and you may move on to the next Once all ranges have been calibrated we recommend ve...

Page 26: ... adjustment tool One AMPTEC OP 300 48 gold plated Kelvin clip lead set Optional One AMPTEC OP 304 48 banana jack calibration lead set E 4 2 Trimmer Potentiometer Adjustment Locations The locations of the trimmer potentiometers referred to as trim pots in this procedure that you will adjust during calibration are shown on Figure 9 below You will be using the trim pots that are located at RV1 RV2 RV...

Page 27: ...n 1 0 Ω resistance standard with 0 005 or better accuracy Adjust the trim pot RV2 to make the meter read 1 00 Ω 100 counts on the display Note that this process will be repeated on the 200 mΩ range with a 0 001 Ω standard after the full scale adjustment is performed 2 Full Scale Adjustment Connect the meter via the measurement test leads across a precision 100 Ω resistance standard with 0 005 or b...

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