| Products > Test Equipment |
| LM399 Voltage Reference, Fluke 289, Gossen 29S, RM303, AN870 |
| << < (5/7) > >> |
| Kleinstein:
The circuit (as far as one can judge from the pictures) looks indeed odd, not like a proper reference circuit. The output is directly from the OP - so excessive capacitance can make it oscillate. The normal way is to take the current for the reference from a bootstrapped reference level of some 10 V or so. This would however need a second OP for the lower voltage settings. |
| Trader:
--- Quote from: masterx81 on December 27, 2020, 12:36:55 pm ---My china lm399 reference after 1.30h of warmup [...] 2.54773 measure 2.46511. --- End quote --- WOW, this is a Huge difference. |
| Martin72:
Why using such suspicious Voltage References ? For calibrating Multimeters ? I let my multimeter calibrate/adjusting external for appx 79 bucks/year, knowing they use a much, much, much more expensive reference for doing it. |
| Trader:
--- Quote from: Martin72 on December 27, 2020, 11:22:47 pm ---Why using such suspicious Voltage References ? For calibrating Multimeters ? I let my multimeter calibrate/adjusting external for appx 79 bucks/year, knowing they use a much, much, much more expensive reference for doing it. --- End quote --- The Chinese product (LM399) and service (calibration) aren't trustable, but I believe in excellent quality and cost/benefit if using the DMMCheck Plus. |
| Trader:
I figure out this chinese LM399 Voltage Reference is MUCH Better as a CURRENT Reference. If you keep the 10V setup (jumps J1-J2, J3-J4, J5-J6) and probe the jumps J7-J12 you have a CONSTANT 1925.8uA or 1.953mA (the difference maybe is the burden voltage) !!! I logged it for +20 minutes (uA, and mA). When I started, decreased 0.1 for <1s, but keep stable the same current for mA and uA all the time, never changing, no ripple (on my DMM). Bellow 2,000 counts is an excellent value for testing all DMMs with the highest resolution. Different jump combinations also gave other interesting lower stable values. A cheap and not too bad stable and precise V, mA, uA reference. Awesome. :-+ |
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