Unitek Peco WELD SENTRY 2, Руководство пользователя

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WELD SENTRY 2 Page 41
CURRENT COIL CALIBRATION
The Weld Sentry has a built-in calibration procedure for the Current Coil measurement circuit. If changing
current pickup type, Coil or Shunt, it may be necessary to calibrate the coil input circuit. Coil Calibration
requires the use of a precision shunt of known resistance. The value used at the factory is. 1 milliohm.
Select Weld Sentry from the Main Menu. Move the cursor to CALIBRATE SENTRY and press [ENTER].
First. check that the Voltage and Current Inputs are less than 3 (see Section previous section on Voltage and
Current Input Adjustments.) then press [
►
] to display the screen:
1. Use weld cables to connect each end of the shunt to each output terminal of the welder.
2. Attach the current pickup coil around one cable.
3. Attach the voltage pickup leads to terminals on the shunt.
4. Fire two "calibration" welds spaced between 0.2 and 2 seconds apart.
The first weld should be at 30% power and the second at 99% power.
5. Check the Low Range and High Range values displayed on the screen.
6. If the values equal the resistance value of the shunt ± 1%, calibration is OK.
If not, the current coil input circuit should be adjusted as follows:
a. Remove the cover and locate the PCB at right side of the unit.
b. Refer to Drawing 4-32603, Assembly PCB, Weld Monitor Module.
c. Adjust each trimpot until displayed values equal the resistance of the shunt ± 1%.
First, adjust R85 for the "Low Range",
then, adjust R92 for the "High Range".
d. After each adjustment repeat the "calibration" weld from step 4,
then check the newly displayed resistance values.
7. Do not fire pulses in rapid succession so that the cables or shunt become hot. Heat will cause the
resistance values to change and the calibration to be inaccurate
.
8. Coil calibration is based on the electrical circuit, Resistance = Volts
÷
Amps
Voltage is measured across the precision shunt.
Current is measured using the current coil.
Calculated resistance = resistance of the shunt when unit is calibrated.
CALIBRATION SUMMARY
1. Calibration Check - Quick and easy, technician not needed, check regularly for good QA.
2. Voltage & Current Input Adjustments - Need DVM, requires technician, precision voltage references,
may want to check yearly for certification.
3. Voltage Measurement Check - Need stable voltage source, requires technician, practical demonstration
of measurement accuracy.
4. Coil Calibration - Need precision shunt, may be required if changing current pickup type.