Digital Multimeter HDM3055 Series Manual

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When you change any of these settings, the sample interval (sample timer in continuous mode) is

increased to be greater than the calculated measurement time. In the continuous mode, attempting

to reduce the sample interval below the calculated value results in an error message. You must then

choose among the various ways you can achieve a smaller measurement time to achieve the smaller

sample interval, such as decreasing the NPLC setting.

Another way to put it is that for continuous mode, sample timer/interval is always controlled by the other

measurement settings.

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Service and Repair

This section contains basic instrument service information.

Cleaning

To prevent electrical shock, disconnect the instrument from AC mains power and disconnect all test

leads before cleaning. Clean the outside of the instrument using a soft, lint-free, cloth slightly dampened

with water.

Do not use detergent or solvents.

Do not attempt to clean internally.

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Electrostatic Discharge (ESD) Precautions

Almost all electrical components can be damaged by electrostatic discharge (ESD) during handling.

Component damage can occur at electrostatic discharge voltages as low as 50 V.

The following guidelines will help prevent ESD damage during service operations:

l Disassemble instruments only in a static-free work area.

l Use a conductive work area to reduce static charges.

l Use a conductive wrist strap to reduce static charge accumulation.

l Minimize handling.

l Keep replacement parts in original static-free packaging.

l Remove all plastic, foam, vinyl, paper, and other static-generating materials from the immediate work

area.

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Troubleshooting

Before troubleshooting or repairing the instrument, make sure the failure is in the instrument rather

than any external connections. Also make sure that the instrument was accurately calibrated within

the last year (see Calibration Interval). The instrument’s circuits allow troubleshooting and repair with

basic test equipment.

CAUTION DO NOT swap the motherboard or the front panel board from one instrument to another.

These boards contain model number and serial number information that uniquely identifies a specific

unit, and boards that are mismatched to the instrument may result in problems with its performance

or warranty.

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Troubleshooting Procedure

1 Remove all remote I/O connections and front panel connections to the instrument. Verify that:

a. the AC mains power cord is securely connected to the instrument and plugged into a live outlet

b. the front panel Power On/Standby switch has been pushed

2 If the standby light below the power switch is not illuminated, re-verify the items above. If all this

is correct, check the AC mains power and then the internal line fuse.

3 Turn the instrument on. If the power-on sequence completes and the display appears to function

properly, verify that the instrument is in local mode, and run the self-test ([Utility] > Test/Admin >

Self-Test). If the display is illegible, replace the front panel board.

CAUTION  Ensure that all connections (front and rear) are removed when self-test is performed.

During self-test, errors may be induced by signals present on external wiring, such as long test

leads that can act as antennas.