Selecting the correct line cycle value (50 or 60 Hz) increases common mode and normal mode noise rejection. The instrument’s function calls support the selection of various integration rates or PLC (power line cycles) values as well as supporting the selection of 50 Hz or 60 Hz for the line cycle rate. PLC values and resolution are detailed in the following table for various measurements.
Measurement |
Measurement Conditions |
Resolution (Digits) |
Reading Rate @ 60Hz line (R/s) |
Power Line Cycles |
Aperture Time (seconds) |
DC Voltage |
Auto Zero Off |
6.5 |
5 |
10 |
0.16667 |
Auto Zero On |
6.5 |
35 |
1 |
0.01667 |
|
Auto Zero Off |
6.5 |
50 |
1 |
0.01667 |
|
Auto Zero Off |
5.5 |
150 |
0.1 |
0.00167 |
|
1K readings, Auto Zero Off |
5.5 |
500 |
0.1 |
0.00167 |
|
1K readings, Auto Zero Off |
4.5 |
3000 |
0.006 |
0.00010 |
|
1K readings, Auto Zero On |
3.5 |
3500 |
0.002 |
0.00003 |
|
DC Amps |
Auto Zero On |
6.5 |
5 |
10 |
0.16667 |
Auto Zero On |
6.5 |
35 |
1 |
0.01667 |
|
Auto Zero Off |
6.5 |
50 |
1 |
0.01667 |
|
Auto Zero Off |
5.5 |
150 |
0.1 |
0.00167 |
|
1K readings, Auto Zero Off |
5.5 |
500 |
0.1 |
0.00167 |
|
1K readings, Auto Zero Off |
4.5 |
3000 |
0.006 |
0.00010 |
|
1K readings, Auto Zero On |
3.5 |
3500 |
0.002 |
0.00003 |
|
2-wire ohms, <10M |
Auto Zero On |
6.5 |
5 |
10 |
0.16667 |
Auto Zero On |
6.5 |
35 |
1 |
0.01667 |
|
Auto Zero Off |
6.5 |
50 |
1 |
0.01667 |
|
Auto Zero Off |
5.5 |
150 |
0.1 |
0.00167 |
|
1K readings, Auto Zero Off |
5.5 |
500 |
0.1 |
0.00167 |
|
1K readings, Auto Zero Off |
4.5 |
3000 |
0.006 |
0.00010 |
|
1K readings, Auto Zero On |
3.5 |
3500 |
0.002 |
0.00003 |
|
4-wire ohms, <10M |
Auto Zero On |
6.5 |
1.4 |
10 |
0.16667 |
Auto Zero On |
6.5 |
15 |
1 |
0.01667 |
|
1K readings, Auto Zero Off |
5.5 |
33 |
0.1 |
0.00167 |
Measurement Functions, Measurement Rate and Resolution
Setting the reading rate sets the integration time (measurement speed) of the A/D converter and the period of time the input signal is measured (also known as aperture). The integration time affects the amount of reading noise, as well as the ultimate reading rate of the instrument. Note that setting the resolution will set default aperture or PLC times.
The integration time is specified in parameters based on the number of power line cycles (NPLC), where 1 PLC for 60Hz is 16.67msec (1/60) and 1 PLC for 50Hz is 20msec (1/50).
The GX2065 has a parabola-like shape for its speed vs. noise characteristics as shown in the figure below and is optimized for the 1 PLC to 5 PLC reading rate. At these rates (lowest noise region in graph), the DMM will make corrections for its own internal drift and still be fast enough to settle a step response <100ms.
Noise Voltage vs PLC rate