Products > Test Equipment
UT61E drift and recalibration
iloveelectronics:
You can also get one of those Chinese voltage reference devices with 4 voltages (2.5, 5, 7.5 and 10V) that has been discussed here at a lower price. In fact I have some of those too (just never had the time to list them on eBay) but I won't be shipping the lithium battery like other sellers. They are really just taking their chances to be honest, because both HK Post and China Post officially do not allow air shipment of lithium batteries.
--- Quote from: Rick Law on November 26, 2013, 01:41:36 am ---
--- Quote from: Lightages on November 25, 2013, 11:53:12 pm ---A DMM Check, or DMM Check Plus are good investments. You mad a small mistake. The DMM Check Plus gives you 5VDC at 0.01% accuracy. This is what is needed to provide a calibration reference for something on the order or 0.1% accuracy. So, it is the perfect thing to use for the UT61E.
It is hard, if not impossible, to get a better spec'd meter than the UT61E for the price. If you buy another meter then you might end up having two meters you are not sure of. If you buy another meter in the future the DMM Check will still be useful and can help confirm the accuracy of both.
If you are considering buying a second multimeter, I would suggest you need to spend around $150 to get much better functionality than the UT61E. What you should be looking for is a safer meter for higher energy circuits to compliment UT61E.
--- End quote ---
You are right! 0.01% and not 0.1%. Typo error on my part.
I don't work on anything more than 20v-30v. I am merely poking around trying to do something fun so it is hard to say I need it.
I am really itching for the darn thing (getting the DMM Check Plus), and I think I am close to talking myself into it. Your "So, it is the perfect thing to use for the UT61E" is helpful in my decision making...
--- End quote ---
Wytnucls:
--- Quote from: BravoV on November 26, 2013, 01:49:06 am ---What kind of voltage references that is used in this kind of DMM ? External or built-in at the main chip ?
--- End quote ---
The band-gap voltage reference (-1.2V) is inside of the UT61E Cyrustek ES51922 chip (75 ppm/C).
So has the 71D, fitted with Cyrustek ES51966, with a slightly better 50 ppm/C.
However, the 71 series uses a Maxim external voltage reference with a 2ppm/c specification (max 5ppm/c).
PedroDaGr8:
The UT61E has a smattering of unpopulated spots which make up the circuit for an external vref (IC, resistors and filter caps). It SHOULD be relatively easy to add if you can figure out the required dividers (mainly I couldn't find a value for the input impedence of the external Vref pin). This is a project that I have had on the back burner for a while now.
Monkeh:
--- Quote from: PedroDaGr8 on November 26, 2013, 08:18:45 pm ---The UT61E has a smattering of unpopulated spots which make up the circuit for an external vref (IC, resistors and filter caps). It SHOULD be relatively easy to add if you can figure out the required dividers (mainly I couldn't find a value for the input impedence of the external Vref pin). This is a project that I have had on the back burner for a while now.
--- End quote ---
Would that be U4?
Please elaborate on the details here, I'm rather curious.
PedroDaGr8:
--- Quote from: Monkeh on November 26, 2013, 10:53:55 pm ---
--- Quote from: PedroDaGr8 on November 26, 2013, 08:18:45 pm ---The UT61E has a smattering of unpopulated spots which make up the circuit for an external vref (IC, resistors and filter caps). It SHOULD be relatively easy to add if you can figure out the required dividers (mainly I couldn't find a value for the input impedence of the external Vref pin). This is a project that I have had on the back burner for a while now.
--- End quote ---
Would that be U4?
Please elaborate on the details here, I'm rather curious.
--- End quote ---
Yeah it is U4 and the unpopulated spots near by. I'll try to find the IC that will work with it when I get home this evening.
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