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| UT61E drift and recalibration |
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| Lightages:
I am curious. What are the costs for the external ref mod and the other parts? It seems to me that this is turning a relatively inexpensive meter into something more expensive and then also needs to be recalibrated after the mods to be of any use. Is it worth it? If it is just for the fun of it then yes of course it is worth it but as far as being of real value? |
| stephenlm324:
As the details for the external Vref are listed earlier I have left that bit out. The 780k ohm resistor (calculated value without external Vref) would be 680k + 100k in series and would probably need adjusting to match each meter, but it would be a good starting point. With the external Vref I am using 947k but again this would probably need adjusting for each meter. If you can get hold of the thermistor without paying a fortune for postage it would be a very cheap way of improving the meter. |
| don.r:
Would these thermistors serve? http://www.ebay.ca/itm/10-pcs-Thermistor-Temperature-Sensor-NTC-MF58-3950-B-100K-ohm-5-DIY-New-/121252422483?pt=LH_DefaultDomain_0&hash=item1c3b352353&_uhb=1 They have a Beta of 3950K vs 3977K for the Vishays you got. They are also 5%. |
| Nuno_pt:
It should be ok. See also the research that was made regarding Ohm and Cap. |
| don.r:
--- Quote from: stephenlm324 on January 01, 2014, 09:52:35 pm ---As the details for the external Vref are listed earlier I have left that bit out. The 780k ohm resistor (calculated value without external Vref) would be 680k + 100k in series and would probably need adjusting to match each meter, but it would be a good starting point. With the external Vref I am using 947k but again this would probably need adjusting for each meter. If you can get hold of the thermistor without paying a fortune for postage it would be a very cheap way of improving the meter. --- End quote --- Would 50R be sufficient for VR1? I was thinking of using a 200R to get an order of magnitude reduction in vibration deviation but still allow for a wider adjustment over time. |
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