ajruiz2000
commented
5 years ago Day two of testing:
Day two of testing resulted in mix results and some inconstancies from day 1:
The fist thing I attempted was to drive a load of approximately the same impendence of the PST. The PST drews about 12uA at 1V. So I drove a 100k resistor at 1V. This resulted in 10uA. I then disconnected the ground and plugged the ground back in to simulate switching voltage. This worked fine.
I then added some capicatance to the load (1uF, .1uF, 220pF) to try to understand if the Keithley did not like capacitive loads. With the .1uF the current measurement looked like it was pulsing between no current and 10uA. Other than this worked fine
I went back to the PST testing. I found different results randomly. Keithley Set up: Vsource = 1V, Current Clamp = 3A. Measured Source = Voltage
First measurement 25mS rise time, very good noise
Second measurement 25ms, Osscilations in the supply line
The third measurement - Similiar to day one of testing (slow rise time)
This different modes could be changed by time or switching measure source . There was real no repeatable way.
Keithley Set up: Vsource = 1V, Current Clamp = 3A. Measured Source = Current Observed a very fast rise/fall time(300ns) but saw pulses of noise on the line, this seemed to be consistent with the current supply switching from sourcing 12uA to nothing. Similar to the results I saw with the capacitive load
The goal of this project is to integrate the Keithley power supply into the Current PST product line and have it be inoperable to the old system. The Keithley has a higher resolution current meter and the integration would add better current monitoring to the PST product line.
System set up; Keithley Set up: Vsource = 1V, Current Clamp = 3A. Measured Source = Voltage Observations - The unit operate correctly switching between two voltages (.5V and 1V) but it was observed the unit had a very slow rise time (in the order of seconds). The oscilloscope confimred that the rise time between the two voltages was approximately 2s. The target rise time is 200-300us.
The noise on the PST power suppy was within specification with 20mV. The measured voltage on the PST was accurate. The PST has full functionality aside from the slow rise time
System set up; This is an identical Test to the previous test with the measured source on the Keithley changed to current. Keithley Set up: Vsource = 1V, Current Clamp = 3A. Measured Source = Current
Observations - The rise time on the PST now is with specification. The noise on the PST power suppy was within specification with 20mV. The measured voltage on the PST was accurate. The PST has full functionality.
One note: the measured current on the Keithley was jumping from 22uA to no reading while running.
An additional feature of the Keithley is that it supports constant current mode. The Keithley will source current as opposed to voltage. The next test I wanted to test the Keithley in Constant Current mode.
System set up; Keithley Set up: ISource = 100uA, Voltage Clamp = 1V. Measured Source = Current No load on the PST.
This was an unusual set up, as I allowed the power supply to rest in the voltage clamp. The supply sourced about 12uA (was not able to supply 100uA - as there was no load) and the voltage was 1.V. The noise on the PST power suppy was within specification with 20mV. The measured voltage on the PST was accurate. The PST has full functionality.
Further results needed. 1) Try to undersatnd why measuring voltage causing a slow rise time. Perhaps some communications with Keithley is needed. 2)I would like to do more tests in constant current mode and understand if the PST will operate when not in the voltage clamp.