Chapter 3: Testing Performance
To test single cursor voltage measurement accuracy with offset
43
To test single cursor voltage measurement accuracy with offset
The single cursor accuracy specification is derived from the Dual Cursor and Offset
accuracy specifications. By testing single cursor accuracy with offset, both Dual Cursor
and Offset accuracies are tested at the same time. This eliminates the need to do
separate tests for each specification.
This test verifies the voltage measurement accuracy of the oscilloscope. The measurement
is made 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
(especially at low voltages). A DC blocking capacitor and a BNC short are used to filter
any noise generated by the power supply so it does not appear at the oscilloscope input.
Specifications
Gain Accuracy: ± 1.25% of full scale at full resolution channel scale
Offset Accuracy: ±(1.25% of channel offset + 2% of full scale + 1 mV) at
full- resolution scale
Resolution: 8 bits, (0.4% of full scale without averaging); or
12 bits, (0.024% of full scale with 32 averages) at full resolution scale
Dual Cursor Measurement: ±(gain accuracy + resolution)
Single Cursor Measurement: ±(gain accuracy + offset accuracy + resolution/2)
Equipment Required
Procedure
1
Connect the equipment.
See Figure 3- 3.
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 Keysight 6114A
Digital Multimeter
(DMM)
Accuracy better than ± 0.1% of reading Keysight 34401A
Cables (2) BNC Keysight 10503A
Adapters (2) BNC (f) to banana (m) Pomona 1269
Adapters (2) BNC tee (m)(f)(f) Keysight 1250-0781
Blocking capacitor 0.18
μF Keysight 10240B
Shorting cap BNC Keysight 1250-0929
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