| Electronics > Metrology |
| Inexpensive Calibration References |
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| IanB:
I have the DMMCheck and I have obtained voltage readings between 4.9995 V and 5.0005 V on different meters I have compared it against. So it seems to conform to its specs. |
| vtl:
You can order texas intruments voltage reference ICs as free samples. 0.05% accuracy and if you look at the bell curve, something like 80% of them are 0.01% or better. Search for REF5050. Just build it up on breadboard or whatever. You can put it in a fancy case for fun if you want. The voltage standards sold on that site are based off the same TI chips. |
| saturation:
If you also need a frequency reference to check the scope against, there are some very low cost DDS function generators, $10-60 [ much cheaper than the Hantek 3x25,or the Instek SFG 1003 I often mention, which cost about $150] that claim accuracy in the ppm, far far more than the scope's stability and can be adequate to use as a check of the horizontal frequency. http://www.ebay.com/itm/UDB1102S-2MHZ-DDS-Function-Signal-Generator-/280779446346?pt=LH_DefaultDomain_0&hash=item415fc2584a For low cost hi-frequency generation http://www.ebay.com/itm/NEW-AD9850-DDS-signal-generator-module-0-40MHz-/170682095715?pt=BI_Signal_Sources&hash=item27bd721863 |
| alm:
Might as well use a micro devboard like an Arduino with a crystal to provide the the reference frequencies, the crystal will be much better than 2%, and division by powers of two is also quite accurate. A variable DC source is usable, although a square wave is easier (don't have to keep switching between GND and DC coupling). You won't be able to verify the highest sweep speeds and vertical settings, the lowest attenuator settings may also be an issue. Bandwidth testing requires more expensive equipment (usually a leveled sine wave oscillator), but it's usually just a performance check without any adjustments anyway. Check the calibration procedure in the service manual. It often requires you to go through all adjustments after the one you changed, so if vertical gain is the first adjustments, you'd ideally have to at least check all other items, since they may be influenced by the change in gain. |
| krivx:
--- Quote from: saturation on January 19, 2012, 06:43:13 pm --- http://www.ebay.com/itm/NEW-AD9850-DDS-signal-generator-module-0-40MHz-/170682095715?pt=BI_Signal_Sources&hash=item27bd721863 --- End quote --- Good to see this recommended, I ordered a similar AD9851 board a few days ago. I'm planning to build it into a small project box. Hopefully it will be portable enough that taking it into the work lab for a transfer calibration won't be a problem. |
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