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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It was the most troublesome, to pick and sort Q FET replacement. Changing The Security Code Connect mains power cable back to meter, turn it on and leave it to warm-up for at least an hour. Capacitors used for stability compensation I used middle sweet spot device for replacement Q U hybrid design block diagram As result of such complex arrangement A front-end does have more input noise compared manua A, and also does not have 1: Modifications log Thermal sensor and manul location: 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 Rear side of the LCD have metal shield, which is obviously not transparent.
As result of such complex arrangement A front-end does have more input noise compared to A, and also does not have 1: Likely, largest contributors to noise performance are C Q U U Here is composite integrator Q,U with integrating capacitor C and pre-amp for comparator circuit U,R,R Table of contents Table Of Contents Electronic input terminal switching Image R trimpot adjutment for offset correction There is special procedure for voltage offset correction, but we will get back to it later.
| Tweaks and mods for HP A digit DMM
To my opinion, this was bit overdue addition, as previous model, A even with official specifications without any tweaks can be more precise and less noisy than Manuak. RMS noise data measurements Note, that on low voltage ranges 0. Vos adjustment trimmer access port in shield cover Connect mains power cable back to meter, turn it on and leave it to warm-up for at least an hour.
Different non-modified HP A performance test, as returned after calibration adjustment, 4-wire resistance.
COTO relay for front end. Sampling rate was equal to 0. Theory Of Operation Dc Current Function Offset Test HP A digital out-guard section.
3457A Digital Multimeter
Modifications for A input amplifier. Final test data rainbow with all tested FET s: Also calibration commands protected by password, which can be configured by user following special procedure. As result there is no mechanical switch on front panel to change terminal side manually.
LCD display removed from assembly. There is no service manual schematics for this module in A documents, but such schematics available in A.
HP 3457A Manuals
Base range, which is 3. Outguard earth-referenced domain contains of: Calibration coefficients are stored in SRAMwhich is powered even if instruments powered off, with help of on-board lithium battery.
Frequency Response Test Wiring Block Preparation I did not want to risk full disassembly, due to risk of killing the only working display.
Direct Mail Order System Options And Accessories R trimpot adjutment for offset correction.
After Q replacement with faster curve manuall original and U more gain input amplifier circuitry started to oscillate with frequency around kHz.
First I check if the adjustment necessary at all why to waste time on extra drift.
File:HP A operating – Hive13 Wiki
Replacement Q matching One kind person my kind regards presented me with thin copper foil with adhesive layer. Rear Lnput Performance Tests standard Instrument Cost of maintenance on these meters is reachable even for hobby users to use a lab working tool.
This module even have same HP part number. This section is added by xDevs. Yes, it also does mean that calibration will be lost if meter too old and battery discharged. This allows to experiment easy without risk of damaging the board taking everything apart for each component swap.