87 & 89 Series IV
Service Manual
24
Special Requirements
DC mV calibration will affect the calibration of all other functions. Therefore, the DC
mV function must be calibrated before calibrating any other function. Similarly, AC mV
must be calibrated before any AC function, but after DC mV. The remaining functions
may be calibrated in any order.
Temperature calibration need only be performed if one of the following components are
replaced during the course of repair: U4 A/D chip, U10 EEPROM, or U100 Reference
Junction Sensor. Temperature is calibrated by making an external temperature
measurement and entering the result into the instrument for calculation of the calibration
constant. The calibration constant is then stored in calibration memory. This is done
using the serial interface. See “Temperature Calibration” section.
When you replace the U10 EEPROM, you must also re-enter the serial number and
model number for the Meter. See “Reprogramming Meter Serial Number and Model
Number” section.
Calibration Inputs
Table 5 lists the input values required for each calibration step.
Note
The column indicating time to settle does not include calibrator settling
time.
Table 5. Calibration Inputs
Step
Value
Frequency
Time to Settle (In Seconds)
DC mV
1
50 mV
DC
16
2
300 mV
DC
7
3
500 mV
DC
7
4
3000 mV
DC
1
Temperature
1
0
1
AC mV
1
500 mV
700 Hz
7
2
300 mV
700 Hz
7
3
100 mV
700 Hz
7
4
50 mV
700 Hz
7
5
3000 mV
700 Hz
7
1. Use 5520A 2-Wire Comp.
2. Zero ohms must use the same calibrator and test leads as all other ohm cal points.
Do not bypass the calibrator with a shorting bar for the zero ohms step.
3. Because of capacitive coupling, readings will be affected by movement of the leads or
operator. Put fingers on UP button and wait for display reading to settle before pushing.
