[time-nuts] Re: repair of an HP E1938A OCXO

Chris Caudle chris at chriscaudle.org
Tue Jul 1 12:43:05 UTC 2025


On Thursday, June 26, 2025 3:47:48 PM Central Daylight Time Bob Camp via time-
nuts wrote:
> There really is no practical way to get an accurate temperature sensor
> inside the oven / on the crystal, without upsetting the operation of the
> device. 

Do you really need to measure the temperature independently?  I don't fully 
understand the control scheme and the differences between C mode and B mode, 
but if you get the oven to the right temperature, will that not set the 
oscillator output back to within spec?  I recall the original description was 
the measurement was with EFC connected to 0V, so I guess you would need to 
know what the nominal value of the EFC should be for on-target frequency.
Am I thinking too simplistically?  Is there a range of oven temperatures where 
the output is close to nominal but the temperature coefficient is not optimal?

-- 
Chris Caudle






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