DCV short zero reading DMM comparison


Graph legend

  • K2001 – 20V, 10 NPLC, AZ on, LS on
  • K2002 – 20V, 50 NPLC, AZ on, LS on
  • 3458A – ? V, 1000 NPLC, AZ off
  • 34970A – 100mV, 200 NPLC

Forum discussion

EEVBlog : DMM noise comparison project

Changelog

  • 4/16: Added radioFlash data
  • 4/17: Added Jf2014 K2001 data
  • 4/17: Added OldNeurons 34461A data
  • 4/17: Added NANDBlog 34410A data

How to add noise measurement data?

1. Have to use interface to log data from meter, such as RS232 or GPIB/LAN.
2. Disable all filtering / math functions on meter. We want get clean data from ADC subsystem. Processing can be done later on PC, in case if needed.
3. Set fixed base range, for example 2V or 10V. Usually it’s most accurate range on meter’s spec.
4. Enable synchronous autozero if there is such in meter.
5. Enable high-impedance mode, if your meter allow selection between 10Meg / HIZ.
6. Set base 10 NLPC.
7. Capture data. Can capture few hours, or leave overnight for example. I can cut stable part, when drift minimal from overall capture.
8. Repeat measurements for other ranges with NPLC settings: fastest NPLC, 0.1 NPLC, 1 NPLC, maximum NPLC.
9. Send your data to ftp://datashort:datashort@ftp.xdevs.com/ (login and password datashort) or post on forums1

Example GPIB query to get data from Keithley 2001/2002:

:SYST:AZER:TYPE SYNC;           // Here we enable autozero sync
:SYST:LSYN:STAT ON;             // Here enable line sync
:SENS:FUNC 'VOLT:DC';           // Measure voltage DCV
:SENS:VOLT:DC:NPLC 10;          // Set NPLC to 10
:SENS:VOLT:DC:RANGE 2;          // Set range manual to 2V
:SENS:VOLT:DC:DIG 8.5;          // Set resolution to 8.5 digits
:SENS:VOLT:DC:AVER:STAT OFF;    // Filter off
:TRIG:SEQ:SOUR TIM;             // Set trigger source from timer
:TRIG:SEQ:DEL 1;                // Set timer to 1 second
:READ?                          // Read data

Example GPIB query to get data from Keithley 2182 nanovoltmeter

:SYST:AZER:STAT ON;             // Here enable autozero
:SYST:FAZ:STAT ON;              // Here we enable front end autozero
:SYST:LSYN:STAT ON;             // Here enable line sync
:SENS:FUNC 'VOLT:DC';           // Measure voltage DCV
:SENS:VOLT:CHAN1:LPAS:STAT OFF; // Analog filter off
:SENS:VOLT:CHAN1:DFIL:STAT OFF; // Digital filter off
:SENS:VOLT:CHAN1:NPLC 5;        // Set NPLC to 5
:SENS:VOLT:CHAN1:RANG 10;       // Set range manual to 10V
:SENS:VOLT:CHAN1:DIG 8.5;       // Set resolution to 8.5 digits
:TRIG:SEQ:SOUR TIM;             // Set trigger source from timer
:TRIG:SEQ:DEL 1;                // Set timer to 1 second
:READ?                          // Read data

RAW CSV-data for every measurement setup run

RAW CSV data location for download

Absolute offset in all measurement sets are subtracted by graph display math. CSV data is not modified and contains non-modified samples.

Sampling rate for 60Hz mains:

1000 PLC 16.67s 20s
200 PLC 3.33s 4s
100 PLC 1.67s 2s
50 PLC 833 ms 1s
20 PLC 333 ms 2.5 rdg/s
10 PLC 167 ms 5 rdg/s
5 PLC 83.3 ms 11 rdg/s
2 PLC 33.3 ms 25 rdg/s
1 PLC 16.7 ms 50 rdg/s
.1 PLC 1.67 ms 500 rdg/s

1 EEVBlog forum link