Hi, the current temperature relationship should be nearly linear, so if 100mA is needed at 20 C ambient and it follows that at 80 C no heating is required, then the heating current will decrease at about 1.7mA/K. cheers, Neville Michie
On 23/11/2007, at 9:33 AM, Didier Juges wrote: > Bruce, > > I have some 4 terminal current sense resistors at work, but they > are very > low values (0.1 ohm and lower), so what I may gain at the sensor I > may loose > in the amplifier. Right now, the 1 ohm resistor and OP-27 give a > voltage > that is way out of the noise, as the curve shows. If I can find more > temperature stable resistors for the instrument amplifier, then I > could use > one of those 4 terminal resistors. I will see what I can get to > improve this > setup. As it is, it may not be extremely accurate in absolute > terms, but it > is precise and probably sufficiently relatively accurate for what I > want to > do. > > What do you think of the 2mA/degree current sensitivity? Is it in the > ballpark? I need to run the test much longer, and over greater > temperature > variations, but I am still tinkering with it... The engineer's > curse :-) > > Didier > >> -----Original Message----- >> From: [EMAIL PROTECTED] >> [mailto:[EMAIL PROTECTED] On Behalf Of Bruce Griffiths >> Sent: Thursday, November 22, 2007 3:28 PM >> To: Discussion of precise time and frequency measurement >> Subject: Re: [time-nuts] HP10811 current versus temperature >> >> Ideally you should use a 4 terminal current sensing resistor >> and a high input impedance instrumentation amplifier. >> A Thomas style 4 terminal resistor in a temperature >> controlled oil bath would be nice, but failing that a low >> tempco 4 terminal resistor will suffice. >> >> Bruce > > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/ > time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
