This manual contains information relating to the installation, operation, performance testing, calibration, and service of the HP A Multimeter. The information. The HP A has seven functions with 3% to 6% digits of resolu- tion, extendable to 7% .. (). Opt Extra Operating and Service Manual. +$ Hp A Pdf User Manuals. View online or download Hp A Operating Instructions Manual, Service Manual.

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This is 48 hours of running time, to ensure that short-term stability of the meter is taken into account.

R help to maintain balance when input is shorted, or in other words — cancel out voltage offset. Everything else, like charge rate switches, counters and control logic integrated on U hybrid ASICor perform auxilary roles reset comparator Ua, switches. Different non-modified HP A performance test, as returned after calibration adjustment, 4-wire resistance.

External parts easy to get damaged Can cause unexpected short circuits, or ESD issues running meter in winter with people wearing charged sweaters. Even with shorted input, when reference noise irrelevant to ADC! Linear power regulator and optoisolation interface between the domains. Adding common mode ferrite choke and removing connections between reference module and mainboard does not need additional explaining either. Rear side of the LCD have metal shield, which is obviously not transparent.

Ac Voltage Function If there is lack of compensation, then amplifier will work normally when input voltage is zero or less then 0. Data from specs for 24 hour and 90 day period was used. HP A input frontend and signal conditioning schematics.


HP 3457A Operating Instructions Manual

Ac Current Function Gain Test This allows to experiment easy without risk of damaging the board taking everything apart for each component swap. Backlight boards with LED diodes installed on mount frame to position light for the edge of display glass.

RMS deviation was calculated, in ppm scale from the average.

R trimpot adjutment for offset correction There is special procedure for voltage offset correction, but we will get back to it later.

Note out of hour specification for negative 3.

COTO relay for front end Image Final test data rainbow with all tested FET s:. I tried to combine modifications in groups, so can test multiple things at same time, when that was possible.

Digital a 1 Assembly Renioval Often modification result was negative performance got worseso reverse modification was required to determine what went wrong. But before that, take a look on the ADC itself. Note that A conversion from ADC is actually 7 digits, but least digit is averaged out and not reported to the front-end, nor the GPIB port remote controller.

Analog Devices ADA Current-limiting resistors are mounted on additional board for the board with four LED s. Much more important fact is, that display is now visible and usable at night time.

Make sure total height of the component in board is not taller then 12 mm, as there is AC module PCBA above the circuitry here. Would require modification of the chassis. HP A with shields installed.

3457A Digital Multimeter

Ac Voltage Performance Tests Hope this can be helpful for other HP A owners. Frequency Counter Performance Tests Ac Convertor Frequency Response Adjustment This is good, even though not as impressive as HP A tweaking.


HP A can also use optional expansion card with multiplexer scanner, to add up to 10 channels for input signals. Disclaimer Redistribution and use of this article or any images or files referenced in it, in source and binary forms, with or without modification, are permitted provided that the following conditions are met: Don’t have an account?

Also each function and mode can be configured either from front panel or remotely over Hp3475a interface. On alternating voltage, A is much weaker than older A.

| Tweaks and mods for HP A digit DMM

Details and modifications were tested on actual single HP A unit, and may or may not work in your particular instrument. HP A input frontend and signal conditioning schematics Image Many of inteface and overall design ideas in this meter are used as a base for later HP A monsters. HP A rear view on modified screen. HP A digital out-guard section Theory of operation, how things work Heart of the meter, ADC built using same principle as A, but now majority of critical components switches, comparator, current setting resistor networks, logics and clock tree is embedded in proprietary hybrid ASIC U Remaining two LED s had current limited by inline resistor, insulated and hidden by thermal-shrink tube.

This opamp provide most of the gain. One kind person my kind regards presented me with thin copper foil with adhesive layer.