Cheap DMM w/Data Logging Memory & PC/BlueTooth Interface - Page 1
Forum section: electronics / testgear

author: MrCreosote
author_rank: Contributor
timestamp: February 26, 2017, 04:32:47 am
content: I have 2 uses for data logging: Battery droop tests and Temperature response and stabilization of heaters and furnaces. Both are very slow data rates (faster becomes "storage oscilloscope" class which, while of interest, I'm not looking for that in particular.)Something like the Radio Shack Data Logger would be ideal for what I am looking for except it uses the PC to log.However, I have found 2 issues:Type-K thermocouple supportData Logging onto internal memory (SDcard would be BONUS)]What is even more frustrating is that it seems there is a real void in BlueTooth Android devices that would utilize a smart phone.I do not want to lug a PC around with my DMM to data log. A smart phone would be as clunky as I'd like to get, but there is a serious lack of such devices.I get the impression that right now, there is a lot of New Product that is beginning to address what I'm looking for.What would I spend? $200 if it really was awesome. If I could get a used Fluke-class that did this, it's hard to say what I'd really spend - more if a scopemeter. I'd give a $50 Chinese DMM a shot too.

author: DaJMasta
author_rank: Super Contributor
timestamp: February 26, 2017, 04:54:59 am
content: Why a DMM? Why not a device designed specifically for thermocouple measurement. I've got a Digi-Sense brand dual channel logger, normally within budget ($10 or so) but I got mine used for something like $35 after shipping... the downloadable software isn't particularly elaborate, and you don't get any graphing on the unit itself, but it's got good battery life, a USB interface, and space for a few thousand readings (I think there's more than one variant).There are a number of brands with inexpensive single channel models, then there are a couple Chinese brands for two channels, but each one seems to have some kind of quirk that really hinders the value proposition, then there are more expensive multi channel data loggers.... but there are definitely non-dmm options that are purpose built for measuring thermocouples.

author: samgab
author_rank: Frequent Contributor
timestamp: February 26, 2017, 05:22:38 am
content: Check out the OWON B35T. It's cheap, has bluetooth data logging to a mobile device, and temp sensor. For about $50.

author: shteii01
author_rank: Frequent Contributor
timestamp: February 26, 2017, 05:44:04 am
content: Hm...Thermocouple to breakout board, to Arduino board:https://www.adafruit.com/products/269Instructions and code are free.(I had three of these in my senior design project, worked fine.)A SD card data logging shield to Arduino board:https://www.adafruit.com/products/1141Out of stock. You probably should get one on ebay. Just make sure it is compatible with Adafruit instructions and code.Bluetooth module for Arduino board:http://makezine.com/projects/connect-an-arduino-to-a-7-bluetooth-serial-module/Arduino board. Get Chinese Uno clone/copy from ebay, should be about 3-4 USD each. It will likely have CH340 TTL to USB chip, get the drivers for it from the internet.See if you can scrounge 9-12 VDC wall wart. Arduino Uno can take up to 20-22? VDC, so if you find 15 or 18 VDC wall wart, that be fine too.

author: MrCreosote
author_rank: Contributor
timestamp: February 26, 2017, 03:40:43 pm
content: Thanks so much for the suggestions!Some replies:TEMP ONLY:I found the Lascar EL-GFX-TC Themocouple Data Logger w/Graphic LCD Display that does it all: stores data, does different thermocouple types, graphic display, and only $130 new.http://www.dataloggerstore.com/product/lascar-el-gfx-tc-thermocouple-datalogger-with-graphic-screen?gclid=Cj0KEQiAlsrFBRCAxcCB54XElLEBEiQA_ei0DInsfJKsApN39trQfzTfut8yFUXEWbue-Uj8vv0nTUwaAq6n8P8HAQThe Lascar EL-USB-TC USB Thermocouple Data Logger EL-USB-TC USB stick with digital readout at $76 new is like a MP3 player and would do the job too.If cheap enough, this route might be the way to go. I guess without the need for DMM input protection and autoscaling circuitry the cost can really be contained.OWON B35TWhen I found this model, I thought SCORE! The Bluetooth to my Galaxy 4 would be acceptable.However how could anyone possibly make a Type K meter that only goes to 400*C? K can do 1300*C. Were they worried about an extra significant digit?Epic Fail.ARDUINO Board:This is very interesting and the cost is nothing. But I would like the convenience of a hand held and don't mind spend some money to get one.SCOPEMETER:I have been putting off finding a used Scope Meter because I have a DRBIII Chrysler scan tool with the PEP module which makes it a big clunky scope meter. But I really will eventually sell it and also don't utilize my Tek 465B - so "downsizing" to a 10 mHz SM is a long range objective. I'm not getting any younger and maybe I need to pull the trigger.I'm assuming there is an affordable used price (would spend more obviously) SM that will do what I want?

author: 2N3055
author_rank: Super Contributor
timestamp: February 26, 2017, 04:18:09 pm
content: Brymen BM525 can log up to 87000 single values and 43000 dual values (it has dual display)..It is 6000 count, dual temperature thermocouple measurements, AC+DC True RMS...I bought it exactly for standalone logging .... it is something about 150€, there is a BM521 that has only one temp channel, and less data points...Also, it is excellent quality, and has good overvoltage protection, so you can actually connect it mains power and leave it there logging without worrying it might explode if transient comes along.. Also with high speed min/max recording, you might use it to catch transients...No Bluetooth though, you take to the PC after you're done and download data via cable..But it seems to me you actually need logging thermometer..As for temperature range, not many multimeters will go over 400C.. Not even all thermometers will... And not many K-type sensors will go that high, you'll have to buy one specified for such temperatures.

author: kwass
author_rank: Frequent Contributor
timestamp: February 26, 2017, 04:32:18 pm
content: Quote from: MrCreosote on February 26, 2017, 03:40:43 pmI have an OWON B35T with the supplied Type K probe and just tested it. My soldering iron got to 410*C, so the specs seem to be selling this meter short. I haven't tried a higher temperature test. I've only used the BT output to my smartphone a few times but it works well and has a decent range.

author: MrCreosote
author_rank: Contributor
timestamp: February 27, 2017, 02:19:22 am
content: BRYMENActually I found it's USA GreenLee version. The Greenlee DML-430A looked like a win, but the problem is that most used ones do not come with the PC interface cable which is almost $150 shipped.It does Type K to 1000*C which is good (Type K continuous duty max temp is about 1100*C)I'd spend $150 used on this one w/interface.kwass,At what temp would the display have to autorange? I was thinking that maybe the spec is for the supplied TC. The question would be what would happen if you subjected the TC to a higher temp. But I'm guessing when it is 4, 40, or 400, it does not autorange, right? Which means it wouldn't autorange to 4000 max to display 1000*C.I really like what you get for he money. It is quite amazing. But the 400 limit is crazy. There are other DMM's that have 700* limits (I think centigrade, otherwise would be about same as 400*C.)Type K is the uber high temp, reliable, accurate, 800# gorilla chromel alumel. (At Robershaw Controls Co. engineering lab, we ran Leeds & Northup glass ink pens with either iron-constantan or chromel alumel. the I-C was for low temp applications. I cringe to think that they probably scrapped all the spools of TC wire when they shut down the plant. The Horror... The Horror...

author: kwass
author_rank: Frequent Contributor
timestamp: February 27, 2017, 06:09:51 am
content: Quote from: MrCreosote on February 27, 2017, 02:19:22 amFirst I should note that I actually have the B35T+, not the plain B35T. The only difference is that the + version has built-in data memory so that you don't need to stay connected to it via BT once you start the logging process. I just tested this meter using the supplied temperature probe:(1) freeze spray got down to -59*C2) butane torch got to 1100*C (probably could have gone higher but I didn't want to cook the probe too much.It's a single fixed range of only integer values.

author: samgab
author_rank: Frequent Contributor
timestamp: February 27, 2017, 08:06:04 am
content: Thanks for that Katie. Looks like it might fit the OP's needs perfectly, especially with the built in data storage as well as the bluetooth in the + version. How many samples can the memory store? I might pick one of these up myself, for the price it looks pretty good. Not to be used on high voltage/high energy installations, but for my sort of use, will fit the bill nicely. Cheers!

author: MrCreosote
author_rank: Contributor
timestamp: February 27, 2017, 03:15:52 pm
content: Yep, looks like OWON B35T+ fits the bill for crazy little money.But I wonder why they quote 400*C in the spec? Maybe an accuracy issue?I'm going to look for some reviews, especially the data logging function and maybe some comment on the 400*C spec. Would love to see an EEVblog review of it (!)The only other improvement would be one that had a graphical display where you could see a small time history as a controller is cycling. (The Lascar EL-GFX-TC duel input temp logger does just that for $150.)In fact, I'd gladly paytwice its priceto have that feature in the OWON.I did find the Redfish iDWM 510 but it is a $200 class device and basically the same as the OWON.

author: DaJMasta
author_rank: Super Contributor
timestamp: February 27, 2017, 05:55:03 pm
content: It could be just that the accuracy spec for that range only goes up to 400C (not the actual max), and it could be (probably more likely) that the supplied thermocouple doesn't use high-temperature rated insulation. If you look around for buying individual thermocouples, it's very easy to find K types that are rated to only a couple hundred degrees C, and it's not because the metals can't handle it, it's because the insulation can't.

author: MrCreosote
author_rank: Contributor
timestamp: February 27, 2017, 08:34:08 pm
content: DajMasta,I believe you are right. 400*C is a common limit for some Type-K TC's. The top end common limit seems to be 1250*C.NEW CONSIDERATION: DMM vs Hand Held DSOWith the price of the B35T+ or BEST+ being a mere $50, NOW for 2-3x more money, can I find a graphical display with he same featres?Of course I checked the ONON 20mHz HH DSO which sells for under $290. But the DSO's are quite different that then DMM's in that the DSO's typically are all about voltage. A DSO that does resistance and temp is not common. And it also seems on-board data logging is not always present.Still, I must now survey the HH DSO's to see what is out there.

author: MrCreosote
author_rank: Contributor
timestamp: February 28, 2017, 10:32:12 pm
content: So now I'm pumped to find a used Fluke 287/9 only to find that it seems that all connectivity to Android or PC use the IR port - AND you have to buy the IR adapter that does this - so you'd need 2 of them, one each for Android or PC USB.If this is true, I'm done with Fluke.