Have you messed with the 4-20 mA loop current? What's its resolution?
That's an extremely useful feature for Instrumentation and PLC troubleshooting. I'd love to have a meter that could do loop power for $60!
I must say that I'd never heard of this feature before doing this research. I haven't used it myself (yet) so all I can do is parrot the specs as listed in the manual:
DC CURRENT (4 to 20mA)
Range: 0 to 100 %
Accuracy: ±0.5 % + 5 dgt
Resolution: 0.01 %
Burden voltage: 1 mV/mA
*Input protection: 0.5A/1000V fast blow ceramic fuse 6.3×32mm on ?A/mA input
* Errata sheet included with meter says this should read 11mV/mA (Same as with the basic DC Current reading)
I didn't include the eratta on this mode before as it was a feature only of this meter. There were two errata sheets included with the meter, one with the two burden voltage changes (DC Current and 4-20mA DC Current), and one applying to all 3?XR series meters. The second refers to the General Specifications > Operating Environment section, and notes that in the 10A ranges the operating temp should be 0-40C @<70% RH instead of 0-50C @<70%. This is one of those things I should have covered in the original post, but I'm scatterbrained.
Test proceedure:
Measuring 4-20 mA Loop Current
1. Set the Function Switch to the loop-current function.
2. Connect the Test Leads: Red to mA, Black to COM.
3. Turn off power to the circuit being measured.
4. Open the test circuit (
-X-) to establish measurement points.
5. Connect the Test Probes in series with the load (to the measurement points).
6. Turn on power to the circuit being measured.
7. Read the display. 0 % = 4 mA, 100 % = 20 mA.
It seems that they essentially measure the current with the same method and accuracy as the DC Current measurement and reformat the data as a percent of accepted range. The manuals have a few odd typos, so I think there was a lot of copy/pasting going on when they put them together. I suspect that the listed accuracy percent and count refer to the mA measurement and not the displayed percent, as it is identical with the basic DC current listed accuracy (See Edit).
I'm just starting to look in to this, so I don't know if this represents a valuable feature or if it lacks in some way that would make a dedicated tester more useful.
Edit: Just rigged up a simple circuit with a target current draw within the 4-20mA range to see what it looks like. I'm using all salvage parts, so tolerances are iffy. Using min/max/avg I get 8.452mA/8.455mA/8.454mA for a minute or so of letting it ride, which is easily explained by the (15 year old AT) power supply and the meter's accuracy, among other things. I flip it over to 4-20mA mode and I get 27.82%/27.84%/27.83%. Math alone yields 27.825%/27.84375%/27.8375% for min/max/avg.
I know this is quick and dirty, but I hope it communicates what the meter actually appears to be doing.
Crikey, at $65 I recon that's gotta be close to one of the best value meters under say $150 on the market.
I've been eyeing off sgi_direct for a while now, they sell Amprobe stuff in bulk at insanely low prices, shame about shipping prices to Australia, otherwise I'd be reselling the damn things myself!
Thanks for sharing the info.
Dave.
Your welcome! Glad to share.