In the +66312A Dynamic Measurement DC Source and 661xC DC Power Supplies User Guide+, Figure B-1, it says to use a 400 ohm resistor for calibration of the 6611C power supply's Low-Range Current Measurement. I assumed that this includes the 6611C with option J05 (i.e., 6611C-J05), a Keysight fully supported/currently manufactured and sold power supply from the 661xC series that is not mentioned in this guide (??). Apparently this is not the case. To be specific:
When I try to use a 400 ohm resistor (399.3 ohms, +/- 20 ppm/C, 5 W) in series with an ammeter as shown in Figure B-1 (B) and follow the procedure for calibration of the Low-Range Current Measurement on page 61 of the guide, I get a test voltage of about 9.76x volts which results in a current reading of somewhere in the neighborhood of 24.4xxxx mA (going from memory here) on my ammeter. When I try to enter this value into the unit as 0.0244... A as part of Step 22, I get an OUT OF RANGE error. Also, as I am going through the calibration procedure after the unit supplies the necessary voltage to the circuit (i.e., after the CAL:LEV P1 is selected after the completion of Step 21), the current reading on the unit itself shows overflow as well, indicating to me that:
1. The unit is trying to supply close to the maximum voltage that would result in a current of less than 20 mA through the resistor load.
2. A 400 ohm resistor is too low of a value to use to calibrate the 6611C-J05 Low-Range Current Measurement.
Based on the Calibration Load Resistor values shown in Figure B-1 for other units in the 661xC series, I believe that the correct value for this resistor should be 500 ohms for the 6611C-J05, since this supply has a max voltage of 10 volts. This is a scaling of the 400 ohm resistor that should be used for the regular 6611C with its 8 volts max to the 10 volts max voltage that the 6611C-J05 is capable of supplying.
If anyone can confirm this assessment or has other ideas, please let me know.
Thanks
When I try to use a 400 ohm resistor (399.3 ohms, +/- 20 ppm/C, 5 W) in series with an ammeter as shown in Figure B-1 (B) and follow the procedure for calibration of the Low-Range Current Measurement on page 61 of the guide, I get a test voltage of about 9.76x volts which results in a current reading of somewhere in the neighborhood of 24.4xxxx mA (going from memory here) on my ammeter. When I try to enter this value into the unit as 0.0244... A as part of Step 22, I get an OUT OF RANGE error. Also, as I am going through the calibration procedure after the unit supplies the necessary voltage to the circuit (i.e., after the CAL:LEV P1 is selected after the completion of Step 21), the current reading on the unit itself shows overflow as well, indicating to me that:
1. The unit is trying to supply close to the maximum voltage that would result in a current of less than 20 mA through the resistor load.
2. A 400 ohm resistor is too low of a value to use to calibrate the 6611C-J05 Low-Range Current Measurement.
Based on the Calibration Load Resistor values shown in Figure B-1 for other units in the 661xC series, I believe that the correct value for this resistor should be 500 ohms for the 6611C-J05, since this supply has a max voltage of 10 volts. This is a scaling of the 400 ohm resistor that should be used for the regular 6611C with its 8 volts max to the 10 volts max voltage that the 6611C-J05 is capable of supplying.
If anyone can confirm this assessment or has other ideas, please let me know.
Thanks
From a historical perspective Keysight (Agilent/HP) does not maintain the User's & Service Manuals up to date with all the nuisances of the "specials" which exist, or might appear in the future. In the early days (of HP/Agilent), virtually all Service/Cal was performed by HP(Agilent), further supporting this perspective.
The 6611C (and family) is particularly sensitive to over-driving the measurement system of the low current range. You are correct, for the "J05" Vout max is 10V, not 8V as is the standard instrument. Therefore, the 400Ω will certainly draw too much current at Vout = 10V. Since this is a Current accuracy measurement, one could either set Vout to 8V (the expected voltage for a 400Ω load) or obtain a 500Ω resistor and use 10V.
Please keep in mind that other setup/specifications "adjustments" many have to be considered when working with "J05" and section "B" of the manual.
Regards,
PeterW