Saturday, April 28, 2012

Mastech MS8218 data logging

I used the logging function for real for the first time last week.  It works well, although the software has now started to crash occasionally under XP.

The crash is not a big deal, because it only occurs when you begin logging.  In other words, if it starts logging, it's fine.  If not, you know before you lose any data.

This would be a total pill if you were waiting for an event before you started logging, because it might crash as soon as you press "Start".  But you could always start logging ahead of the event.

The only other problem is that the software does run out of buffer at about 45 hours, max.  If you want to do weeks of logging - like I did - you have to save and reset the buffer every 2 days tops or lose data.

Oddly enough, what little I have found on the MS8226T meter indicates it does not have this problem.  It still has the RS-232/USB interface - same style as the MS8218.  In fact, aside from the 50,000 count display, I'm hard-pressed to find any real difference between them.

The 8226 does have a temperature function, and even comes with a thermocouple.  This is good, as I was really looking for a temperature meter with a peak hold, because I'm doing a lot of temperature monitoring that I can't always keep a close eye on right now.  I can get the VC99 for about $34, or the 8226 for about $60.

Unfortunately, the adapter looks like it's permanently attached to the thermocouple, so it may only accept special thermocouples.  I would have to get one to see if the adapters I have gotten from other meters could be used with an 8226.  The VC99 accepts a standard bladed thermocouple native.

(I know that Dave over at EEVblog did not like the VC99.  Everything he said is spot-on correct, I'm sure.  I love Dave, he's the best damn reviewer out there.  They probably are cheap, somewhat poorly built, and have sucky battery life.

But for what I want, it seems the best option.  Not many cheap meters have temperature, peak hold, and the ability to take a standard K-type thermocouple with no accessory adapter.  Dave covers nearly everything, but not the presence or absence of min/max/peak, and didn't give the VC99 any credit for being the only one to take a standard thermocouple.)

It's also possible the "new"? software from an 8226 would operate the 8218.  In which case I could "upgrade" my 8218 to seconds/minutes/hours logging from the current seconds-only software.  I may give it a go.

I could always buy both the VC99s and the 8218s.  I may just do that.  If I was on the road all the time, in all kinds of weather conditions, I'd want 1 excellent meter.  If the meter is getting frozen or heated, or bashed around, and I can't get another one if it breaks, by all means.

But in my lab, I'd rather have 14 cheap meters and one good meter than one excellent meter.

Why?  2 DMMs are tied up right now with battery tests.  3 are presently doing temperature tests for me.  I could use one more for ambient temperature monitoring, so that's 4 just for that test, or 6 in total.  That's nearly all I have on hand right now.

If I had more loggers, I could be doing more battery tests, or do more data collection per test than I can do now.

Plus I do not mind having meters for different reasons.  Three VC99s would be nice for temperature logging, as they accept standard thermocouples, but can also do other things.  Two 8226s for data logging would probably cover logging, as well as filling in for temperature and other things.  One 50000 count 8218 for current logging or whatever is probably fine.

Plus they're so cheap - why not?  As I argued in my previous post, they are plenty accurate.  Especially when you consider they are never used outside of room temperature, or at least not very much.

For temperature accuracy, +/-1*C is not going to change anything at all.  Voltage and resistance are dead easy.  Current is hardly any more difficult until you get to the microampere range, in which case having one pretty good meter is covering that.  And so on.

If I do invest in the 8226 or VC99, I'll try to remember to post what I find.

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