CALIBRATION
5-12
Necessary Equipment
Instrument Critical Specifications Recommended Model
Time Interval Counter Time Interval Accuracy SRS SR620
1 ns max
DC/AC Voltmeter 5 1/2 digit DC accuracy Fluke 8840A with Option -09
True RMS AC to 100 kHz
Standard Resistors Resistance known to 0.01% SRS calibration parts
Q accuracy known to 25 ppm
R0 95.300 kΩ
R1 5.970 kΩ
R2 374.0 Ω
R3 25.10 Ω
Fixture to BNC Adapter SRS SR728
Calibration Conditions
Warm up time: At least 30 minutes
Temperature: 23 °C ±2 °C
1. Amplitude Calibration
This procedure calibrates the output amplitude at the different frequencies and output voltages. To adjust
the calbytes, press the [Calibrate] key until the message "cl i" (where i is an integer) appears in the left
display. The present value of that calbyte will appear in the right display. The [UP ARROW] and
[DOWN ARROW] frequency keys step through the different amplitude calbytes. New values are entered
using the numeric entry keys.
1) Connect the AC/DC volt meter across the two sides of the fixture. A small piece of wire inserted in
each side of the fixture is a convenient way to connect the DVM. Do not connect either end to ground.
Set the meter to AC volts, autoranging. Set the SR715/720 to its default conditions ([Recall] [0]
[ENTER]). Set the unit to constant voltage mode.
2) Set the amplitude and frequency for amplitude calbyte 0 (0.10 V and 100 Hz). If the value is not within
2% of the nominal value, enter the new calbyte using the formula:
New Calbyte = (V nominal / V measured) x (Present Calbyte) rounded to the nearest integer
3) Verify that the amplitude is within 2% of the nominal value. See the table below for the acceptable
limits for each amplitude.
4) Repeat steps 2 and 3 for 120 Hz, 1 kHz, 10 kHz, and 100 kHz (Calbytes 1, 2, 3 and 4) at this
amplitude (0.10 V). Calbyte 4 (100 kHz) should be set to zero for the SR715.
5) Repeat steps 2 - 4 for each amplitude in the table. At each amplitude, repeat the measurement for
each frequency, starting with 100 Hz and increasing to 10 kHz (SR715)or 100 kHz (SR720).
Remember that the 100 kHz calbytes should be zero for the SR715.
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