Recommended Test Equipment - Keithley 7708 User Manual

Example reading limit calculation
The following is an example of how reading limits have been calculated. Assume you are testing the 10V DC range using a 10V
input value. Using the Model 27xx one-year accuracy specification for 10V DC of ± (30ppm of reading + 5ppm of range), the
calculated limits are:
Reading limits = 10V ± [(10V × 30ppm) + (10V × 5ppm)]
Reading limits = 10V ± (0.0003 + 0.00005)
Reading limits = 10V ± 0.00035V
Reading limits = 9.99965V to 10.00035V
Calculating resistance reading limits
Resistance reading limits must be recalculated based on the actual calibration resistance values supplied by the equipment
manufacturer. Calculations are performed in the same manner as shown in the preceding example, except, of course, that you
should use the actual calibration resistance values instead of the nominal values when performing your calculations.
For example, assume that you are testing the 10k Ω range using an actual 10.03k Ω calibration resistance value. Using
Model 27xx one-year 10k Ω range accuracy of ± (100ppm of reading + 6ppm of range), the calculated reading limits are:
Reading limits = 10.03k Ω ± [(10.03k Ω × 100ppm) + (10k Ω × 6ppm)]
Reading limits = 10.02894k Ω to 10.03106k Ω

Recommended test equipment

Table 2 summarizes recommended verification equipment. You can use alternate equipment as long as that equipment has
specifications at least as good as those listed in
uncertainty of each measurement.
Table 2
Recommended verification equipment
Fluke 5700A Calibrator:
DC voltage
100mV:±14ppm
1.0V:±7ppm
10V:±5ppm
100V:±7ppm
1000V:±9ppm
Fluke 5725A Amplifier:
AC Voltage, 50kHz: 700V, ±375ppm
Keithley 3930A or 3940 Frequency Synthesizer:
1V RMS, 10V RMS, 1kHz, ±5ppm, steady state and burst modulation
General Radio 1433-T Precision Decade Resistance Box:
10 Ω to 400 Ω , ±0.02%
Miscellaneous Equipment:
Double banana plug to double banana plug shielded cables (2)
BNC to double banana plug shielded cable
NOTE: The Fluke 5725A amplifier is necessary only if you wish to verify the 750V AC range at 50kHz. Verification at
220V and 50kHz using only the 5700A calibrator is adequate for most applications.
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Table 2. Keep in mind, however, that calibrator uncertainty will add to the
AC voltage (1kHz, 50kHz)
100mV:±200ppm
1.0V:±82ppm
10V:±82ppm
100V:±90ppm
700V:±85ppm
Resistance
100 Ω :±17ppm
1k Ω :±12ppm
10k Ω :±11ppm
100k Ω :±13ppm
1M Ω :±18ppm
10M Ω :±37ppm
100M Ω :±120ppm