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UT61E drift and recalibration

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Monkeh:
$5 of GDTs fixes the input protection (really, the fuses are fine. Really. You're not measuring 800VDC current with this meter. If you are, just think again.).

I think it's still a pretty capable meter for the price, but like any tool it has its limits and they must be known.

don.r:
I'll be adding a couple of MOVs when I do the VRef mod. I don't normally measure anything over 150V so a 300V MOV should do it. Long term drift will only be known over the course of time maybe a year after the mod is done. It only takes a few minutes to do the work as all the pads are there. I will say that it really is only a 2200 count meter without the mods and you could pick up good 6000 count for the same money. I have another mod in mind however that is only capable with this meter. I'll let you know what it is when I have finished it.

sorin:

--- Quote from: don.r on February 05, 2014, 06:26:39 am ---I will say that it really is only a 2200 count meter without the mods and you could pick up good 6000 count for the same money.

--- End quote ---
Which model do you refer?


--- Quote from: Monkeh on February 05, 2014, 04:52:23 am ---$5 of GDTs fixes the input protection

--- End quote ---
What you mean with "GDTs" ?

don.r:
An Amprobe AM-270 for high voltage use or a used Fluke.

GDT = Gas Discharge Tube. You can use those or spark gaps or MOVs. Spark gaps and GDT operate at 1KV and above usually and I have no plans to take this meter anywhere near there so I'll stick to a 275V MOV (clamps at 600VDC).

Nuno_pt:
Hi all,

I think that was some tutorial about changing the PTC that he brings with GDT or MOV, but can't find it.

The long term stability can only be view after an year after the Vref mod, against a calibrated source, DMMCheck Plus after the annual calibration, or something better.

Trimming the resistance side it's much more trouble since it controls V + Ohm, you've to mess with all the resistors in that chain + R34.
The 100Ohm rage it's adjust by itself, just put a lower value.

Still studying the capacitance side.

You can spend maybe another $40 in mods, the time doesn't count it's just for fun, so I think that for $80, 4.5 digits with 22.000 counts but more precise and stable, and maybe better on Ohm and pF, it's hard to beat for the price.

You can always by a HP 3478A, or others for around $150, but not portable, maybe not much space on the lab, etc...




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