Fluke 525A Service Manual page 50

525A
Service Manual
3. Allow a few seconds for everything to stabilize, then press the Enter key. In a few
4. Connect channel A of the 1281 to the Resistance Standard as follows:
5. Connect channel B of the 1281 to the 5520A as follows:
6. Connect 525A to the 5520A as follows:
7. Set the 5520A to source 50 Ω.
8. Using the two channels on the DMM, calculate the actual value of the 5520A's
42
moments the following is displayed on the PC:
Input ~50 Ohms, Enter the actual value when stable:
The ~50 indicates that the desired resistance is about 50 Ω. The actual resistance is
not as important as the accuracy with which the value is known. The method
described below uses the 1281 to establish a ratio between the 5520A output and the
742 to improve the accuracy with which 5520As output resistance is known.
1. Connect I+ of the DMM to the high side of the current input of the Resistance
Standard.
2. Connect I- of the DMM to the low side of the current input of the Resistance
Standard.
3. Connect the high side (HI) of the DMM sense input to the high side of the sense
output of the resistance standard.
4. Connect the low side (LO) of the DMM sense input to the low side of the sense
output of the resistance standard.
a. Connect I+ of the DMM to the high side of the current input of the 5520A.
b. Connect I- of the DMM to the low side of the current input of the 5520A.
c. Connect the high side (HI) of the DMM sense input to the high side of the sense
output of the 5520A.
d. Connect the low side (LO) of the DMM sense input to the low side of the sense
output of the 5520A.
a. Connect HI INPUT 4W RTD Ω jack of the 525A to the high side of the current
input of the 5520A.
b. Connect LO INPUT 4W RTD Ω jack of the 525A to the low side of the current
input of the 5520A.
c. Connect the HI SENSE 4W RTD Ω jack of the 525A to the high side of the sense
output of the 5520A.
d. Connect the LO SENSE 4W RTD Ω jack of the 525A sense input to the low side
of the sense output of the 5520A.
output. This is done by using the ratio of a known standard to the output of the
5520A. The 1281 can be used to calculate the ratio or proceed as follows.
Ratio = A/B
RA = RS/Ratio
Where:
A = The reading taken from channel A on the DMM.
B = The reading taken from channel B on the DMM.
RS = The value of the resistance standard (in this case 10K).