Chapter 3: Testing Performance
To test voltage measurement accuracy
3–7
To test voltage measurement accuracy
Th is te s t v er ifi e s t he v o lt age m e as ure m en t a c c ur ac y o f t he i n s tr um en t. T he m ea su r em e nt i s m a de
using dual-cursor automatic measurement so that offset errors are not a factor.
A power supply provides a reference voltage to check voltage measurement accuracy. The actual
supply voltage is monitored for accuracy using a NIST-traceable voltmeter. A dc blocking
capacitor and a BNC short are used to filter any noise generated by the power supply (especially
at low voltages) so it does not appear at the oscilloscope input.
Specification
Only the dual-cursor specification is tested.
Single Cursor Measurement:
±(gain accuracy + offset accuracy + resolution/2)
Dual Cursor Measurement:
±(gain accuracy + resolution)
Gain Accuracy
: ± 1.00% of full scale at full-resolution channel scale
Resolution: 8 bits, (0.4% of full scale without averaging); or
12 bits, (0.024% of full scale with 32 averages) at ful-resolution scale
Offset Accuracy
: ±(1.00% of channel offset + 1% of full scale) at full-resolution scale
Equipment Required
Procedure
1
Connect the equipment.
See figure 3-4.
a Use a BNC-to-banana adapter to connect a BNC cable to the power supply.
b Connect a BNC tee to the other end of the cable and connect the tee to channel 1 of the
oscilloscope.
c Connect another BNC cable to the tee at the oscilloscope and connect a BNC tee to the
other end of the cable.
d Connect the blocking capacitor to the BNC tee and connect the BNC short to the blocking
capacitor.
e Connect a BNC-to-banana adapter to the same BNC tee and connect the adapter to the
DVM input.
Equipment Critical Specifications Recommended Model/Part
Power Supply 7 mV to 30 Vdc, 0.1 mV resolution Agilent 6114A
Digital Multimeter
(DVM)
Better than 0.1% accuracy Agilent 34401A
Cables (2) BNC Agilent 10503A
Adapters (2) BNC (f) to banana (m) Agilent 1251-2277
Adapters (2) BNC tee (m)(f)(f) Agilent 1250-0781
Blocking capacitor 0.18
µF Agilent 10240B
Shorting cap BNC Agilent 1250-0774
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