Stanford Research PRS10C (Lady Heather 6.08)

[Ohm_My]

Hello All,

I've been using LH along with my rubidium oscillator and am curious as to how LH retrieves the "Life" reading. I assume this is a total cumulative up-time reading for the unit. I did some extensive reading in the Service Manual for the PRS10C but did not see how to query for this value.

Any assistance is appreciated.

[texaspyro]

The PRS10 firmware updates the FC value in EEPROM every 12 hours or on every power cycle.  It also logs the counts in EEPROM.   Do a little math on the numbers and you get an estimate on the power-on hours...  a clever wench be Lady Heather!  Estimate will be off if the device is not left on continually or you do a lot of manual writes of the FC value. 

[matthuszagh]

The PRS10 firmware updates the FC value in EEPROM every 12 hours or on every power cycle.  It also logs the counts in EEPROM.   Do a little math on the numbers and you get an estimate on the power-on hours...  a clever wench be Lady Heather!  Estimate will be off if the device is not left on continually or you do a lot of manual writes of the FC value.

Where does 12 hours come from? The manual says:

Occasionally while the unit is operating (at about 20 minutes after power-on and once a day there after) the program will write a new value to EEPROM to correct the value for crystal aging.

Also relevant:

FC!? will return four values (separated by commas), the number of power cycles the unit has undergone, the number of times the FC pair has been written to EEPROM...

So to estimate the operation time, it seems like you'd take the 2nd number, subtract the first and that would give you the number of full days of operation. That ignores manual updates to the frequency control, so it's only accurate if the number of FC manual updates is sufficiently low.

That said, the first two numbers from my unit's fc are: 79,10910. My estimate would imply 30 years of continuous operation, which seems unlikely. Yours gives more like 15 years, which seems much more reasonable.