HTC DM 91 Operator's Manual - Page 6

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4.6.1 Connect the black test lead to COM jack and the red to V/Ω/CAP jack.

4.6.2 Set the rotary switch at the desired Ωrange position.

4.6.3 Connect test leads across the resistance under

measurement.

4.6.4 You can get reading from LCD.

NOTE:

When only the figure'1' or '-1' is displayed, it indicates over-range situation and the higher range has to be selected.

For measuring resistance above 1MΩ, the mete may take a few seconds to get stable reading.

When the input is not connected, i.e. at open circuit, the figure '1' will be displayed for the over-range condition.

When checking in-circuit resistance, be sure the circuit under test has all power removed and that all capacitors have been discharged

fully.

At 200MΩ range, display reading is around 10 counts when test leads are shorted. These counts have to be subtracted from

measuring results. For examples, when measuring 100 MΩ resistance, the display reading will be 101.0 and the correct measuring

result should be 101.0-.1.0=100.0 MΩ.

the value scale to be measured is unknown beforehand, set the range selector at the highest position.

4.7 MEASURING CAPACITANCE

4.7.1 Connect the black test lead to COM jack and the red to V/Ω/CAP jack.

4.7.2 Set the rotary switch at the desired F range position.

4.7.3 Before inserting capacitor under measurement into

capacitance testing socket, be sure that the capacitor

has been discharged fully.

4.7.4 You can get reading from LCD.

4.7.5 When capacitor testing is needed frequently, put the plug of capacitor testing equipment (spare parts) into COM and V/ Ω/CAP jack, put

the capacitor foot into two long socket of capacitor testing equipment, then capacitor testing is ready.

To avoid electrical shock, remove test leads from measurement circuit before measuring

the capacitance of a capacitor.

NOTE:

1. At the small capacitor range, the reading will include the small value because some influence from the distribution of test leads, but it will not

influence the accuracy of measuring.

2. It takes time to get a steady reading while measuring high capacity.

4.8 TRANSISTOR TEST

4.8.1 Set the rotary switch at 'hFE' position.

4.8.2 Determine whether the transistor under testing is NPN or PNP and locate the emitter, base and collector leads. Insert t he leads into

proper holes of hFE socket on the front panel.

4.8.3 Read the approximate hFE value at the testing condition of base current Ib10uA and Vce 3V.

4.9 DIODE TESTING

4.9.1 Connect the black test lead to COM jack and the red to V/Ω/CAP jack. (the polarity of red lead is '+')

4.9.2 Set the rotary switch at the

4.9.3 Connect the red lead to the anode and the black lead to

the cathode of the diode under testing.

4.9.4 You can get a reading from LCD.

NOTE:

1. The meter will show approximate forward voltage drop of t the diode.

2. If the lead connections is reversed, only '1' will be displayed.

4.10 CONTINUITY TEST

4.10.1 Connect the black test lead to COM jack and the red to V/Ω/CAP jack.

4.10.2 Set the rotary switch at the

4.10.3 Connect test leads across two points of the circuit

under testing.

4.10.4 If continuity exists (i.e. resistance less than about 70Ω), built-in buzzer will sound.

NOTE:

If the input open circuit, the figure '1' will be displayed.

4.11 MEASURING FREQUENCY

4.11.1 Connect the black test lead to COM jack and the red to V/Ω/CAP jack.

4.11.2 Set the rotary switch at the 200KHz range position.

4.11.3 Connect test leads across the source or load under measurement.

4.11.4 You can get a reading from LCD.

NOTE:

Reading is possibly at input voltage above 10V rms, but the accuracy is not guaranteed.

In noisy environment it is preferable to use shield cable for measuring small signal.

4.12 MEASURING TEMPERATURE

4.12.1 Set the rotary switch at the ℃ range position.

4.12.2 The LCD will sow the current temperature of the environment.

4.12.3 When measuring temperature with thermocouple, temperature probe for this meter can be used. Insert 'K' type thermocoup le into the

WARNING

F range position.

range position.