Characterizing heating element - Page 1
Forum section: electronics / projects

author: Rachie5272
author_rank: Regular Contributor
timestamp: October 30, 2016, 06:16:31 pm
content: I'm doing a scientific study, and need to characterize the voltage, current, and temperature relationship of a specialized heating element. Basically, I want to run the element through hundreds of power profiles, and measure the temperature at regular intervals.I'm using a passive infrared module as the temperature sensor. It's a very nice piece of kit with a USB interface; no problems here. The power supply is on a USB -> RS-232 interface. It's a bit clunky, but more or less works. A Python program is responsible for controlling the setting power supply parameters, and reading back the measured power and temperature.Unfortunately, the power supply isn't quite powerful enough. I'm using a very nice Agilent E3631A supply, with +6V 5A and ±25V 1A rails. Neither rail is quite enough.So, I need a new power supply. I'm currently looking at a GW Instek PSP-2010 (20V 10A), and a Mastech HY3020MR (30V 20A). Both have RS-232, but I don't think either have anywhere near the accuracy or resolution of the Agilent. I'm not entirely sure I need this, though.Can anyone offer a recommendation on a power supply?

author: plesa
author_rank: Frequent Contributor
timestamp: October 30, 2016, 07:23:48 pm
content: What about used E3634A or 6642A, for remote operation they have better support in general than Mastech/GW I suppose.If everything will be PC controlled, why not add IR camera like Flir E4/E8 for image or video capture?

author: 2N3055
author_rank: Super Contributor
timestamp: October 30, 2016, 08:27:17 pm
content: You must setup measurement uncertainty requirements for your experiment.. GW Instek PSP-2010 looks like it can be easily programed through RS232, and if it's specifications are "good enough" for your purpose, you can use that.. Or like plesa said, try to get more "serious" instrument, that will give you more confidence in measurement results...So first, start designing the experiment, setup accuracy requirements, and if you can get away with less precision and higher measurement uncertainty, you can use less expensive equipment..If, when designing experiment, you come to a calculation that you'll have to very precise, then you will have to find a way to get higher spec equipment, maybe borrow it, rent it whatnot..But if you want to buy instrument, it might make sense to buy it not only for this experiment, but for later too.. In that case, if budget allows you, you get instrument as good as you can get, so come tomorrow, you could use it for something else too..

author: Rachie5272
author_rank: Regular Contributor
timestamp: October 31, 2016, 12:17:21 am
content: I looked into a Flir camera, but they simply aren't fast enough for what I need. I got a high speed,tiny spot size optical pyrometer instead. All the sensor data gets logged in a database for easy processing.Is GPIB easy to use? I would need a USB adaptor (pricey), and I'd be worried about getting stuck with proprietary software. I'm leaning towards RS-232 simply because it's for more universal.

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: October 31, 2016, 02:03:23 am
content: How many volts and amps do you need?You might be able to use your E3631A to control another Agilent power supply. For example I have a 6654A that will accept a 0-5V input. In this mode it works as an amplifier with a gain of 12.Regards,Jay_Diddy_B

author: plesa
author_rank: Frequent Contributor
timestamp: October 31, 2016, 11:16:10 pm
content: Quote from: Rachie5272 on October 31, 2016, 12:17:21 am25fps is not enough? OK, above 25fps it restricted.GPIB is easy, chcek the xDEVs.com for RPi and GPIBhttps://xdevs.com/guide/ni_gpib_rpi/I must say that it is much easier than operatin multiple instruments over rs232, because you have all of them on same bus, instruments are not so sensitive to syntax.Like Jay mentioned, if you needs to buy new PSU only for this project consider something cheaper controlled by your E3631A power supply.Look also for some TDK, Sorensen PSU, often they have remote controlled current and voltage (over bus or by external voltage).If voltage controlled voltage source is enough like Jay mentioned use e.g Meanwell SPV series, crappy but for heating OK.

author: kxenos
author_rank: Frequent Contributor
timestamp: November 01, 2016, 12:57:46 am
content: Get them to buy an AIM-TTI CPX400SP programmable power supply. 400 watts power with precision and accuracy better than any keysight/agilent one. I have my cpx200 for 17 years without calibration and it is still better than 0.1%. My new cpx200dp is better than 0.001% for 2 years now.

author: Rachie5272
author_rank: Regular Contributor
timestamp: November 01, 2016, 03:51:50 pm
content: How does controlling one power supply from another work? Can this still measure the voltage and current?

author: plesa
author_rank: Frequent Contributor
timestamp: November 01, 2016, 05:50:07 pm
content: Quote from: Rachie5272 on November 01, 2016, 03:51:50 pmDepends on your level of precision. But in general yes ( but only voltage or current not both) , you know the transfer function (0-5V on input can control 3-27V on output).

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: November 01, 2016, 08:45:39 pm
content: Quote from: Rachie5272 on November 01, 2016, 03:51:50 pmOn my HP/Agilent 6654A there are terminals on the back for analog programming. In this power supply, and many other HP supplies, the programming voltage is reference to the positive output terminal, not ground. From the analog input to the output the gain is x12 with this power supply, so 0-5V is 0-60V. So I would connect the output of a low power supply as the programming input. In this case the programming supply is working as a DAC and providing level shifting and isolation. This does introduce additional errors. The output can be measured with a DMM to eliminate the error.Regards,Jay_Diddy_B

author: Crystal-JU-206
author_rank: Newbie
timestamp: November 02, 2016, 02:10:12 am
content: You are so crazy about study!!!I think I should learn a lot from you.

author: Rachie5272
author_rank: Regular Contributor
timestamp: November 02, 2016, 05:46:03 pm
content: I ended up going with a BK Precision 1687B. 36V, 10A, USB connection. The serial commands are a tad primitive, but it should work well enough.