100 OHM PRT readout suggestions - Page 1
Forum section: electronics / general

author: itsbiodiversity
author_rank: Regular Contributor
timestamp: October 16, 2017, 03:25:45 pm
content: Hello all! I am new to the forum; however, I am not new to the field. I am looking for some opinions on 100 OHM PRT readouts that have treated you right over the years. Of course I am very familiar with the Fluke 1502 readout, and it is my favorite among those that I have used. I am looking for more affordable options than the 1502, if there are any. The unit must be capable of measuring 4-wire RTD measurements with very little uncertainty. Current price of a 1502 is over $2k, and the unit only reads resistance / temperature. I would really appreciate some recommendations of multimeters with good resistance accuracy so that the meter can be used for other functions than temperature. I do not mind performing calculations of the temperature using the readout resistance.

author: sokoloff
author_rank: Super Contributor
timestamp: October 16, 2017, 03:34:03 pm
content: Quote from: itsbiodiversity on October 16, 2017, 03:25:45 pm"Very little uncertainty" is unfortunately not a spec.What spec are you willing to live with?

author: ap
author_rank: Frequent Contributor
timestamp: October 16, 2017, 04:00:03 pm
content: My recommendations are:Keithley 2001 or 2002 (I m using a dedicated 2002 e.g. to measure the temperature of a resistance standard array). 3458A is fine too, but pretty expensive though.If lower budget is desired then e.g. Keithley 2700.Advantage of all of tese is that tehy are universla meters rather than just (imo overpriced) dedicated meters. Unless you use e.g. a 25 ohms PRT.

author: itsbiodiversity
author_rank: Regular Contributor
timestamp: October 16, 2017, 04:05:55 pm
content: To be general, less than 0.08 degrees C. The probe I have is a fluke 5627 100 ohm prt and has a temperature coefficient of 0.00385 ohm/ohm/degC nominal. I may be wrong just estimating here so that would be around 0.0002 ohm accuracy or better to achieve the results I am looking for. Please correct me if I am wrong making that calculation as I am on the go at this moment.I will mention that I have used the 3458a in the past and love it also. Are there any recommended multimeters that measure below 100 ohm with accuracy of this level? I would prefer the 3458a over the 1502a even though the price is higher due the the available functions.

author: VintageNut
author_rank: Frequent Contributor
timestamp: October 16, 2017, 06:25:51 pm
content: The DMM7510 has a 1-ohm 7 1/2 digit full-scale resistance range.

author: nfmax
author_rank: Super Contributor
timestamp: October 16, 2017, 07:11:54 pm
content: I have used Labfacilty pt100 instruments for many years and really like them. I 'rescued' a Tempmaster 100 which was being thrown out with a couple of probes (one semi-standard!) when they closed down at work. An ice point check read -0.02 deg C with the semi-standard probe, both instrument and probe were supplied in 2004. Very reliable and very helpful company. Their current range of instruments are described here:https://www.labfacility.com/media/attachment/file/b/e/bench_top_instruments_guide_1.pdfEdit: I forgot to say they all support individual probe calibration factors for highest accuracy

author: Kleinstein
author_rank: Super Contributor
timestamp: October 16, 2017, 08:00:11 pm
content: Quote from: itsbiodiversity on October 16, 2017, 04:05:55 pmThe typical PT100 changes resistance by 0.385 Ohms per degree (K or C). So 0.08 K corresponds to 0.03 Ohms. So the requirements are not that high. Most better DMMs with a 200 Ohms 4 wire resistance more should be OK, as the typical test current is at 1 mA in this range.

author: itsbiodiversity
author_rank: Regular Contributor
timestamp: October 16, 2017, 08:43:00 pm
content: Quote from: Kleinstein on October 16, 2017, 08:00:11 pmThank you for pointing that out I went off the rails by a few hundred!