[time-nuts] Temperature sensors and quartz crystals
jimlux
jimlux at earthlink.net
Sun Jun 4 21:55:30 EDT 2017
On 6/4/17 4:59 PM, Attila Kinali wrote:
>
>> Where did you get the idea to use a 1 k load for an AD590?
>
> Jim was refering to a circuit _he_ used in a satellite. Not to your circuit.
>
We've also used 3k. It's more about supply voltage, expected
temperature range, and the ADC you're using (if any). 1k is handy if
you're running off 5V and are feeding a 1 volt full scale ADC - room
temp is 0.3 V. Note that the *minimum* voltage across an AD590 is 4V,
so if you've got a 3V supply, you're out of luck.
10k gives you 3V at room temp, and is quite ok into a 5V ADC, as long as
your supply is at least 7-8 volts.
There is self heating to worry about if you have a high supply voltage
(12V @ 0.3 mA is 3.6 mW), but realistically, all sensors have that
problem (unless you are using a PRT in some sort of bridge that nulls
the current)
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