Usage:
A lever is used to open the jaws of the ammeter to allow the conductor to be inserted. The spring-loaded jaws are then closed around the conductor to measure the current. A trigger switch is used to turn on the ammeter. This trigger can be locked in the on or off position. When the turn-on trigger is released, the last reading is held for 5 seconds. This allows measurements to be taken in limited access areas where the display is not visible. A zero control is also provided for DC operation. Power for the ammeter is supplied by four AA batteries located inside the handle of the ammeter.
NOTE: The 8T900 Clamp-On Ammeter is a replacement for the 6V4910 Clamp-On Ammeter.
Optional Items for Use With The AC/DC Clamp-On Ammeter
Specifications
MEASUREMENT RANGE: 0 to 1200 amperes.
READOUT METHOD:
1 - 1200 amperes: Direct readout digital display on handle of ammeter case.
0 - 1 amperes, remote readout of 0 - 1200 amperes, 0 - 199 amperes with 0.1 ampere resolution: Use a 6V3030, 6V7070 or 6V7800 Digital Multimeter to read output of ammeter.
ACCURACY DC, PULSED DC (SCR WAVEFORM) AND AC (15 to 100 Hz):
1 - 1200 Amperes: +20°C (+68°F) to +60°C (+140°F): Typical: ± 2% of reading ± 1 digit (± 2 digits on AC); Maximum: ± 3% of reading ± 1 digit (± 2 digits on AC)
-12°C (+10°F) to +19°C (+67°F): Typical: ± 1% to +4% of reading ± 1 digit (± 2 digits on AC); Maximum: 0 to +5% of reading ± 1 digit (± 2 digits on AC)
0 - 1 ampere: ± 4% of reading ± 1 digit (± 2 digits on AC) using a Caterpillar Digital Multimeter with 6V6014 Cable.
1 - 500 amperes: AC (100 Hz to 1 KHz): ± 6% of reading ± 1 digit (± 2 digits on AC).
FREQUENCY RESPONSE:
Readout AC Mode: 20 Hz to 1 kHz.
Output Jacks: DC to 1 kHz.
RESOLUTION: 1 ampere using digital display.
OPERATING TEMPERATURE: -12°C to +60°C (+10°F to +140°F) .
STORAGE TEMPERATURE: -30°C to +70°C (-22°F to +158°F).
HEATING LIMITATION: The AC component being measured must not exceed an ampere (rms) frequency product of 1000A kHz.
WITHSTAND CAPABILITY: Core-to-output 600 VDC or 480 VAC.
OUTPUT JACKS:
Output: ± 0.5 V at 500 Amperes
Accuracy: ± 1% of reading plus above stated accuracy.
Noise: 1 mV rms typical, 2 mV rms maximum.
Recommended Load: 100 K ohms minimum.
READOUT: 3 1/2 digit liquid crystal display.
READOUT HOLD TIME: 5 seconds.
CABLE APERTURE SIZE: 19 mm (.75") closed diameter.
POWER: Four "AA" batteries.
BATTERY LIFE (POWER ON): Alkaline 30 hours typical, 20 hours minimum. Mercury 60 hours typical, 40 hours minimum.
LOW BATTERY INDICATOR: Arrow appears on digital display.
SIZE: 230 mm x 115 mm x 37 mm (9" x 4.5" x 1.5").
WEIGHT: 0.45 kg (1 lb) with batteries.
CORE DEMAGNETIZER: Automatic core demagnetizer is activated whenever power is turned off and on.
Connections And Controls
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Do not use on bare conductors or on voltages of more than 600 VDC or 480 VAC. |
- 1. Jaws - The jaws open to accept conductors up to 19 mm (.75") in diameter. The jaws are insulated except at core closure.-
- 2. Core Closure - Opens to allow conductor to enter the aperture. The core closure area must be tightly closed when taking measurements. Keep this area free of foreign material. Avoid snapping the jaws which could damage the core closure or core.
- 3. Aperature - Opening in center of core which holds the conductor when measurements are being taken. The aperture is insulated except at the core closure points.
- 4. Jaw Lever - Lever used for easy one-hand opening of the jaws. When the ammeter is hand-held, this lever can be pulled with the fingers.
NOTE: Always release lever slowly to prevent snapping the jaws.
- 5. Power Trigger Switch (shown depressed) - Depress switch with finger to take readings. Switch turns on ammeter when fully depressed. Automatically demagnetizes the core when depressed. Digital readout value is automatically held for 5 seconds after power trigger switch is released.
- 6. Slide Lock - Locks the power trigger in the ON or OFF position when moved toward the power trigger.
- 7. Current Direction arrow - When the reading on the digital display shows a positive reading (negative sign is not showing), then conventional current is flowing in the direction of the arrow from positive to negative.
- 8. AC-DC Mode Switch - Used for selecting AC or DC readout operation. This switch has no effect on the voltage output terminals on the end of the handle. Moving this switch allows both the AC and DC components of the current to be measured in the same wire.
- 9. Battery-Low Indicator - An arrow shows at the top of the digital display when battery requires replacement. Ammeter will not be accurate if this arrow is showing in the display.
- 10. Digital Display - Liquid crystal 3 1/2 digit, digital display shows current value in amperes. AC current is shown in RMS amperes. A negative (-) sign shows when the current is flowing opposite the direction of the current arrow on the case.
- 11. DC Zero Adjust - Adjust Sets the digital display to 000 before taking DC readings, has no effect on operation in the AC mode.
- 2. Core Closure - Opens to allow conductor to enter the aperture. The core closure area must be tightly closed when taking measurements. Keep this area free of foreign material. Avoid snapping the jaws which could damage the core closure or core.
- 12. Output Jacks - These jacks are for use with a Caterpillar Digital Multimeter and 6V6014 Cable. The red jack is positive and the black jack is negative when the current is flowing in the direction of the current arrow on the case. Voltage will be AC or DC, or composite AC on DC depending on the current being measured. Each component can be measured by switching from ACV to DCV on the digital multimeter.
- 13. Battery Access Screw - Remove a single Phillips screw to remove the battery holder for replacement of the batteries. The battery holder slides out to accept four "AA" batteries.
Battery Installation
(1) Four "AA" size 1 1/2 volt batteries are needed to power the ammeter. Either alkaline or mercury batteries should be used. The battery life for both types is listed in the specifications. The batteries for new ammeters are packed in the foam surrounding the ammeter.
(2) Loosen the battery access screw in the end of the handle labeled "REMOVE TO REPLACE BATTERIES". Remove the end cap and slide the battery holder out of the handle.
NOTE: Always support the battery holder when removing and installing batteries to prevent unnecessary stress on the flexible leads.
(3) Snap the four batteries into place in the holder, being careful to match the + and - polarity signs on the batteries with those on the holder. Slide the battery holder back into the ammeter case as far as possible. Replace the lid and tighten the access screw. Pull the ammeter power trigger. Digits should show on the digital display.
Operation Instructions
IMPORTANT: The following warnings and notices must be observed in order to prevent personal injury and/or possible damage to the instrument.
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Before each use, inspect the ammeter for cracks, breaks or crazes in the insulation, especially in the aperture area. Replace defective parts immediately. |
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Hands, shoes, and the floor must be dry when making measurements. Do not use the ammeter during humid or damp conditions which could affect the dielectric withstanding voltage of the instrument. |
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Do not use the ammeter on bare conductors or attempt to measure any voltage exceeding 600 VDC or 480 VAC. |
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Do not use the ammeter when the case of the ammeter is wet. |
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Always release the jaw lever slowly to avoid snapping the jaws. Be sure the core closure points are clean and free of foreign material. Be sure the core is completely closed before taking measurements. |
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Do not use aromatic hydrocarbons or chlorinated solvents to clean the ammeter case. |
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Nearby current carrying conductors can cause errors in measurements due to stray magnetic fields. |
(A) Measuring DC Current Using Direct Readout Method
(1) Put AC-DC mode switch (1) in the DC position. Turn on the ammeter by depressing power trigger switch (2). The switch can be locked in the ON position by moving slide lock (3) toward trigger switch (2). Make sure the low battery arrow indication is not showing on the digital display. If it is, replace the batteries.
(2) For maximum accuracy, allow the ammeter to warm up for 60 seconds in the ON position before taking any measurements. To take a measurement, select a point along the conductor to be measured where the influence of stray magnetic fields from adjacent conductors or large ferrous metal objects is at a minimum.
(3) Hold the jaws of the ammeter 50 to 100 mm (2 to 4 inches) away from and at right angles to the conductor to be measured. Adjust DC ZERO ADJUST control (4) until the digital display reads 000. As long as the ammeter is held close to the original position it was in during zero adjustment, the influence from stray magnetic fields and the earth's magnetic field will not affect the readings.
(4) Open the jaws of the ammeter by depressing jaw lever (5). Check to be sure the core closure area is clean before taking any measurements. Move the ammeter in position so the wire being measured is positioned in the core closure opening as shown. Release lever (5) slowly to avoid snapping the jaws. To ensure the most accurate readings, always put the conductor in the center of the aperture. Make sure the core closure is tightly closed before taking readings.
(5) Observe the current reading in amperes on the digital display. A positive reading (- sign is not showing) indicates the DC current is flowing in the direction of the arrow on the case.
(6) When measuring high DC currents or transient currents resulting from power turn on, the core of the ammeter may become magnetized. This will cause an error if low value DC currents are then measured. To prevent an error in measurement, always remove the ammeter from the conductor before reading lower currents. Turn the ammeter off and on several times to demagnetize the core. Readjust the DC ZERO ADJUST control each time before taking a reading. If practical, do this before measurement of all DC currents.
(B) Measuring DC Current Using A Digital Multimeter For Remote Readout
Current less than 1 ampere can be measured to a resolution of 0.1 ampere with the ammeter if a digital multimeter is used in place of the readout on the ammeter. Higher currents up to 1200 amperes can also be measured using the digital multimeter.
(1) Use a 6V6014 Cable to connect the ammeter to the digital multimeter as follows. Connect red cable plug (1) to the red output terminal on the ammeter, and black cable plug (2) to the black output terminal on the ammeter. Connect the positive (+) terminal of double plug (3) to the V-Ohms terminal on the multimeter, and the negative (-) terminal of double plug (3) to the COM terminal of the multimeter. This will make the multimeter reading positive (+) when the current is flowing through the circuit in the direction of the arrow on the case of the ammeter.
(2) Set Function/Range switch (4) on the multimeter to the 200m DCV (200 millivolt) scale. The digital display will now read in amperes and tenths of amperes up to 199.9 amperes. The 2 DCV scale can be used for currents up to 1200 amperes if desired; however, on this scale, the decimal point will not be in the correct location and should be ignored.
(3) To take measurements, do steps 1 through 6 of the procedure "MEASURING DC CURRENT USING DIRECT READOUT METHOD" shown on page 6. The only difference now will be that the current will be read on the multimeter display instead of the ammeter display.
(4) For greater accuracy when taking low current measurements, the reading can be multiplied by looping a number of turns of the conductor through the aperture. To obtain the actual current, divide the reading on the multimeter by the total number of turns through the aperture. This method can be used with the ammeter readout as well as with the multimeter readout.
(C) Measuring AC Current Or AC On DC Current Using Direct Readout Method
(1) Put AC-DC mode switch (1) in the AC position. Turn on the ammeter by depressing power trigger switch (2). The switch can be locked in the ON position by moving slide lock (3) toward trigger switch (2). Make sure the low battery arrow indication is not showing on the digital display. If it is, replace the batteries.
(2) For maximum accuracy, allow the ammeter to warm up for 60 seconds in the ON position before taking any measurements. No zero adjustment is necessary when measuring AC amperes. The display may read 1 or 2 amperes. This is due to pickup of stray AC fields and a small amount of normal amplifier noise.
(3) Select a point along the conductor to be measured where the influence of stray magnetic fields from adjacent conductors and large ferrous metal objects are at a minimum. Open the jaws of the ammeter by depressing jaw lever (4). Check to be sure the core closure area is clean before taking any measurements. Move the ammeter into position so the wire being measured is in the core closure opening as shown. Release lever (4) slowly to avoid snapping the jaws. To ensure the most accurate readings, always put the conductor in the center of the aperture. Make sure the core closure is tightly closed before taking any readings.
(4) Read the current in amperes RMS on the digital display.
NOTE: If the jaws of the ammeter are clamped around both the supply and return conductors in a circuit, such as a power cord, opposing magnetic fields will cancel each other and cause the ammeter to read zero current.
(D) Measuring AC Current Using A Digital Multimeter For Remote Readout
Current less than 1 ampere can be measured to a resolution of 0.1 amperes with the ammeter if a digital multimeter is used in place of the readout on the ammeter. Higher currents up to 1200 amperes can also be measured using the digital multimeter.
(1) Connect double plug (1) of the 6V6014 Cable to the V-Ohms and COM terminals on the multimeter. Connect single plugs (2) of the cable to the output jacks on the end of the ammeter handle. Polarity is not important for AC measurements.
(2) Set Function/Range switch (3) on the multimeter to the 200m ACV (200 millivolt) scale. The digital display will read direct in amperes and tenths of amperes up to 199.9 amperes. The 2 ACV scale can be used for currents up to 1200 amperes if necessary; however, on this scale the decimal point will not be in the correct location and should be ignored.
(3) To take measurements, do steps 1 through 4 of the procedure "MEASURING AC CURRENT USING DIRECT READOUT METHOD" shown on page 8. The only difference now will be that the current will be read on the multimeter display instead of the ammeter display.
NOTE: The display will read a noise value when no current is being measured. For a more accurate reading, especially for low value measurements, subtract this noise value from the current reading.
(4) For greater accuracy when taking low current measurements, the reading can be multiplied by looping a number of turns of the conductor through the aperture. To obtain the actual current, divide the reading on the multimeter by the total number of turns through the aperture. This method can be used with the ammeter readout as well as with the multimeter readout.
Checking The Accuracy Of The 8T900 Ammeter
(A) Equipment Needed
(1) A variable DC power supply, 21 Volts maximum at 2 amperes or a 12 Volt 2 ampere battery. [Two 18 gauge or larger, insulated copper wire leads (not shown).]
(2) 6V3030 or 6V7070 Digital Multimeter, .25% minimum accuracy, with standard test leads or equivalent.
(4) 6V6124 Calibration Coil (part of 6V6180 Calibration Group) - fits smaller aperture of 8T900 and 6V4910 Ammeters than the 5P8609 Coil provided in the 5P8608 Calibration Group. Do not use 6V6124 Coil to calibrate 5P969 or 2P5540 Ammeters.
(B) Accuracy Check Procedure
This procedure should be performed at least once a year to ensure the ammeter is within specifications. The following checks must be made with all components stabilized at a room temperature of 25°C ± 5°C (77°F ± 9°F).
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The following instructions must be followed exactly or the results will not be correct. Also, the 6V6124 Calibration Coil must be used to get accurate results with this Ammeter. |
(1) Connect the 21 Volt power supply (1), or a 12 Volt battery, to 12 Volt DC terminals (2) on the calibrator with 18 gauge or larger wire. Connect the (+) positive supply lead to (+) positive and the (-) negative supply lead to (-) negative.
(2) Connect digital multimeter (3) to VOLTMETER terminals (4) using the meter test leads. Set the meter to the 20 VDC range.
(3) Connect 6V6124 Calibration Coil (5) leads into coil jacks (6); red plug in the (+) positive and black plug in the (-) negative.
(4) If a power supply is used instead of a battery, turn it on and set the output voltage at 18 Volts (12 Volts can be used if 18 Volts is not available, but maximum calibration current will be lower). NEVER USE MORE THAN 21 VOLTS OR DAMAGE TO THE AMMETER WILL BE THE RESULT.
If a battery is being used, make sure it is fully charged. Open the jaws of the ammeter and inspect the core closure points to be sure they are clean and free of all foreign material. If necessary, clean the points. Close the jaws slowly to avoid snapping them.
(5) Depress the power trigger on the ammeter and lock the trigger in the ON position. Let the ammeter warm up for several minutes. If the low battery indicator appears during the test, replace the batteries.
(6) Put AC-DC Mode Switch (7) in the DC position. Open the jaws of the ammeter and place the 6V6124 Coil in the aperture of the ammeter. Make sure the arrow on the coil points in the same direction as the arrow on the ammeter. Close the jaws slowly. Move the coil slightly to be sure it is loose in the aperture and the jaws are tightly closed.
(7) Put the ammeter in the position shown so 6V6124 Calibration Coil is on current selector switch knob (9). Keep the ammeter and the coil in this position during the entire test procedure.
NOTE: The 6V6124 Calibration Coil is accurate when used in one position only. It must be held straight out from the end of the ammeter as shown. Any change from this position will cause an error in the readings. To help keep the coil in this position during test, put the coil on the CURRENT SELECTOR switch knob with the Ammeter in the location as shown.
(8) Adjust DC ZERO control (8) until the digital display reads 000.
(9) Turn CURRENT SELECTOR knob (9) to the number one position for the lowest current setting. Press PUSH TO CALIBRATE button (10) and make a comparison between the ammeter reading and the reading on the digital multimeter. The multimeter will show the actual calibration current. On the 20 VDC scale of the digital multimeter, current can be read directly in amps, except the decimal point is not in the correct location.
NOTE: Do not hold down PUSH TO CALIBRATE button (10) too long or the coil and calibrator will heat up.
(10) Repeat the previous step for each CURRENT SELECTOR setting 2 through 6. IMPORTANT: When going from a higher current setting to a lower current setting, always turn the ammeter off then back on; then zero the ammeter before taking a reading. This will demagnetize the core and prevent error in the reading.
(11) If the ammeter reading is not within specification, the ammeter must be calibrated as shown in the following procedure.
Calibration Of The 8T900 Ammeter
(A) Equipment Needed
In addition to the equipment shown on page 10, the following equipment is required for calibration.
- 1. A fixed or variable filtered DC power supply capable of supplying 12 Volts at 2 amperes. This power supply must be used in place of the battery if one was used for the Accuracy Check Procedure (only one power supply is required for calibration.)
- 2. 6V3030 or 6V7070 Digital Multimeter (two required for calibration).
- 3. 6V6014 Cable - for connecting ammeter output jacks to second multimeter (a multimeter deluxe lead kit can be used in place of this cable).
- 2. 6V3030 or 6V7070 Digital Multimeter (two required for calibration).
(B) Calibration Procedure
Always perform the Accuracy Check as shown on page 11 before calibrating the ammeter. If the ammeter is within specification, do not attempt to calibrate it.
The following calibration must be performed with all components stabilized at a room temperature of 25°C ± 5°C (77°F ± 9°F).
(1) Use a knife blade to pry up on one side of decal (1) on the side of the ammeter. Carefully remove the decal to expose the three adjustment screws.
(2) Perform Steps 1 through 7 of the Accuracy Check Procedure shown on page 11 but with the following changes.
a) Replace the battery with the filtered DC power supply if a battery was used.
b) In Step 3, set the power supply voltage to 12.00 Volts DC.
c) Use the 6V6014 Cable (or 6V3032 Deluxe Lead Kit) to connect the output jacks on the handle of the ammeter to the second multimeter. Connect the red (+) jack to the V-Ohms terminal on the multimeter, and the black (-) jack to the COM terminal on the multimeter. Set Function/Range switch (2) to 2 DCV.
(3) Release the ammeter power trigger to turn off the ammeter; then depress the trigger again and lock it in the ON position. This will demagnetize the core to ensure an accurate reading.
(4) Use the DC ZERO control on the handle of the ammeter to adjust the digital multimeter reading to 000. If the DC ZERO control does not have enough range, coarse zero control (3) on the side of the ammeter can be adjusted. Use a small screwdriver to adjust this control. After adjustment, both the ammeter and the multimeter must read 000.
(5) Turn CURRENT SELECTOR (4) to position 6 with the calibrator power supply set at 12.00 Volts. Press PUSH TO CALIBRATE button (5); multimeter (6) must read 4.00. Adjust calibrator power supply (7) if necessary to maintain this reading. Do not keep the PUSH TO CALIBRATE button depressed for long periods or the coil will heat up.
(6) While the PUSH TO CALIBRATE button is depressed and multimeter (6) reads 4.00, observe the reading on multimeter (8). This reading must be .406. Be sure the 6V6124 Calibration Coil is straight out from the end of the ammeter. Use a small screwdriver to adjust output calibration screw (9) until an ammeter output of .406 is indicated on multimeter (8).
(7) With the PUSH TO CALIBRATE button depressed and multimeter (6) reading 400 (disregard the decimal point), the display on the ammeter handle must read 406. If it does not, use a small hex head wrench to adjust display calibration screw (10) to get a reading of 406 on the ammeter.
(8) Repeat Steps 3 through 7 without making any adjustments. If all readings are correct, the ammeter is calibrated. If the readings are not correct, repeat the calibration procedure. After the ammeter has been calibrated, the Accuracy Check Procedure shown on page 11 should be used to verify correct calibration at various current levels.
(9) Replace the decal on the side of the ammeter case. If the decal is damaged, replace it with a new one (Caterpillar FORM SEES5657).
Repair Of The 8T900 Ammeter
If the ammeter appears to be operating incorrectly, perform the Accuracy Check Procedure shown on page 11 and then the Calibration Procedure shown on page 13. If this does not correct the problem, the ammeter should be returned to the manufacturer for service. A letter should accompany the returned unit indicating the problem and the date of purchase from Caterpillar. Ammeters less than one year old will be repaired under warranty, except for abuse. The cost of out-of-warranty repairs will be charged to the owner. The repair centers for the ammeter are:
F. W. Bell6120 Hanging Moss Road
Orlando, Florida
U.S.A. 32807
Telephone No. (305) 678-6900