Shakakasa HP A original Q matching. Rear Terminal Assembly Removal HP A input amplifier after all modifications Image Now turn the meter again, front panel facing to us, remove top plastic cover and under it we can find top shield, holder of the multiplexer board. Reference voltage source is same module from A, using LM ovenized buried zener circuit. LCD display removed from assembly.
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Shakakasa HP A original Q matching. Rear Terminal Assembly Removal HP A input amplifier after all modifications Image Now turn the meter again, front panel facing to us, remove top plastic cover and under it we can find top shield, holder of the multiplexer board. Reference voltage source is same module from A, using LM ovenized buried zener circuit.
LCD display removed from assembly. Carefully lift rear side of the shield, disconnect hpa from rear terminal and turn screen up. Options And Accessories Data from specs for 24 hour and 90 day period manusl used.
There is no service manual schematics for this module in A documents, but such schematics available in A. Calibration hpa performance verification This section is added by xDevs. Experimentally, I figured out that there is indeed balance offset. That mean each modification test is full reassembly, few hours warmup and then multiple hours for datalogging each low range separately! Offset Test Limits Inner protection shields Image 7: I tried to combine modifications in groups, so can test multiple things at same time, when that was possible.
Wondering, if that is design issue of HP A, or simply particular unit trait. Inguard isolated section has next circuits: This was required to enable trimpot RP1 setting for both negative and positive gate voltage. Last calibration date or history of the unit is unknown. Table below present measured data after calibration adjustment and performance verification.
Front Panel Inputs I used middle sweet spot device for replacement Q Calibrated vs same Fluke A on January 21, Yes, it also does mean that calibration will be lost if meter too old and battery discharged. File:HP A operating — Hive13 Wiki Redistributions of files in binary form must reproduce the above copyright notice, this list of conditions, link to this page https: Measurement noise data plots Few practical notes about modifications After Q replacement the complete input amplifier balance had to be adjusted and re-calibrated.
HP A with shields installed. This is 48 hours of running time, to ensure that short-term stability of the meter is taken into account. Connect mains power cable back to meter, turn it on and leave it to warm-up for at least an hour. Often modification result was negative performance got worseso reverse modification was required to determine what went wrong. File:HP A operating manual. This means that disassembly and cover removals not required for adjustment and calibration with few exceptions, covered later.
Electronic input terminal switching Image Hmm, hold on a moment? TOP Related Articles.
Download HP 3457A docs - Various electronics service manuals
Powerful Measurement Management The A combines superb analog measuring capability with equally powerful measurement management. More than readings or whole measurement sequences can be stored in the A for convenient and fast measurement throughput. The present dmm setup can be stored in the non-volatile state memory for convenient reconfiguration of the dmm. The power of total electronic calibration, including AC volts, makes it easy to maintain instrument performance. Finally, programmable front-rear terminal switching lets you measure two separate inputs without a scanner. For example, if you want to make a measurement on a 9 volt DC signal with.
HP 3457A Digital Multimeter Service Manual