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iMo:
FYI - thermistor Beta calculated from the "44000 thermistor series" DS values (Steinhart-Hart):
It fits the common 3975 (2k2 and 5k) and 3695 (10k) betas at 25/85C..
Hydron:
A quick check with a multi turn trimpot set to the 25C and 85C values (from the table above) for each thermistor option suggests that imo's numbers are bang on - "2.2k" really should be 2252 ohms, and it's probably safe to assume that the 4400x thermistors are indeed the parts intended to be used.
My DMM6500 seems to have the same options (the manual calls out the same 4400x thermistor part numbers), and it applies for the KS 3446x/70 meters too (going by the datasheet at least) - are these three just what DMM manufacturers have standardised on supporting? Lucky for Omega if so!
Is a little disappointing that you don't have the option of custom R and beta on the newer meters at least (though adding that support with a script that would be relatively easy on the DMM6500).
TizianoHV:
--- Quote from: imo on January 24, 2023, 08:39:34 pm ---FYI - thermistor Beta calculated from the "44000 thermistor series" DS values (Steinhart-Hart):
It fits the common 3975 (2k2 and 5k) and 3695 (10k) betas at 25/85C..
--- End quote ---
I confirm that my 34970A uses 10K thermistors with beta=3695 (ask how I know :palm:)
iMo:
I enabled the temperature feature in my meter and tried with 6 random 10k NTCs off my junkbox (3+2+1 different type sets, unknown Betas). The quick test:
a) the 3 were +0.12, +0.2, +0.27C off the LM35 I've been using (+16bit adc), at ambient in open air, aprox 1cm apart, with cold 34401A
b) the 2+1 were +1..+2C off.
Btw. the RTD mode allows to dial in the R0 and alpha.
alan.bain:
One mystery which I never solved was what is measurement type 9. These are the measurement modes I know about. The firmware definitely references a mode 9. The measurements are classed depending on how the measurement works so e.g. class 0 is DCV like - straight integration over a time window, class 1 is AC like - so sum of squares of measurements over short interval then sqrt (nobody really wants a straight time average of RMS values), class 2 is time/frequency which uses the AD channel 1.
The mystery mode 9 is DCV like. Maybe I forgot something obvious....or is there something else to discover?
1 DCV (class 0)
2 ACV (class 1)
3 ohm 2W (class 0)
4 ohm 4W (class 0)
5 DC A (class 0)
6 AC A (class 1)
7 frequency (class 2)
8 period (class 2)
9 unknown ?? (class 0)
10 continuity (class 0)
11 diode (class 0)
12 temp 4 wire RTD (class 0)
13 temp 2 wire RTD (class 0)
14 temp t/c (class 0)
15 temp thermistor (class 0)
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