Digital Multimeter HDM3055 Series Manual

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Step 4: Press Range to select a range for the measurement. You can also use the [+], [-], and

[Range] keys on the front panel to select the range. (Auto (autorange) automatically selects the

range for the measurement based on the input. Autoranging is convenient, but it results in slower

measurements than using a manual range. Autoranging goes down a range at less than 10% of

range and up a range at greater than 120% of range. For capacitance measurements only, when

autorange is off, the instrument does not report an overload for readings greater than 120% of range.

Overload only occurs when the algorithm times out because the applied capacitance is too large for

the algorithm to measure. If you apply a DC voltage or a short to the input terminals in capacitance

measurement mode, the instrument reports an overload.

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Step 2: Press

on the front panel.

Step 3: To null–out the test lead capacitance:

l Disconnect the + and - test leads probe end from the test circuit, and leave open.

l Press Null. The DMM will now subtract this null value from capacitance measurements.

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Capacitance

This section describes how to configure capacitance measurements from the front panel.

Step 1: Configure the test leads as shown.

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Step 5: Use the Units softkey to display temperature in degrees Celsius, degrees Fahrenheit, or Kelvin.

Thermistor Requirements

The DMM converts the measured thermistor resistance to temperature using the Steinhart-Hart thermistor equation:

1?T = A + B (Ln(R)) + C (Ln(R))3

A, B, and C are constants provided by the thermistor manufacturer and derived from three

temperature test points.

R = Thermistor resistance in Ω.

T = Temperature in degrees K.

Important: Use only a 5 k? 44007-type thermistor. This type thermistor has constants of A = 1.285e-3, B = 2.362e-4,

C = 9.285e-8. Using an incorrect type of thermistor can result in errors greater than 20 °C for a temperature being

measured of 100 °C.

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Step 4: Press Aperture and choose the number of power-line cycles (PLCs) to use for the

measurement. Only 1, 10, and 100 PLC provide normal mode (line frequency noise) rejection.

Selecting 100 PLC provides the best noise rejection and resolution, but the slowest measurements:

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Step 3: Press Probe and choose the probe type.

Additional settings for each probe type are described in the sections below.

For the RTD 2w or RTD 4w Probe Type...

If you choose to use an RTD, the menu will have a softkey to specify the RTD's resistance at 0

degrees Celsius (R0 ). Default 100 Ω

For 2-wire measurements, an Auto Zero softkey is available.

Auto Zero: Autozero provides the most accurate measurements, but requires additional time to

perform the zero measurement. With autozero enabled (On), the DMM internally measures the  

offset following each measurement. It then subtracts that measurement from the preceding reading.

This prevents offset voltages present on the DMM’s input circuitry from affecting measurement

accuracy. With autozero disabled (Off), the DMM measures the offset once and subtracts the

offset from all subsequent measurements. The DMM takes a new offset measurement each

time you change the function, range, or integration time. ( There is no autozero setting for 4-wire

measurements.)

For the Thermis2w or Thermis4w Probe Type...

For the Thermis2w probe type, an additional Auto Zero setting is available.

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Step 2: Press [Temp] on the front panel. The following menu appears.

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4-wire Temperature:

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Temperature

This section describes how to configure 2-wire and 4-wire temperature measurements from the front panel.

Temperature measurements require a temperature transducer probe. The supported probes are 2-wire and

4-wire RTDs, 2-wire and 4-wire thermistors.

Step 1: Configure the test leads as shown.

2-wire Temperature:

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Negative Resistance Measurements

Under certain conditions, the instrument may report negative resistance measurements. These may

occur in 2-wire and 4-wire resistance measurements or continuity measurements.

Conditions that may cause negative ohms values include:

l Changes in Front/Rear switch contact resistance

l Reversed Sense Hi and Lo leads

l Circuits with external bias or thermal voltages at circuit connections

l Changes in measurement connection after a NULL operation

Under the same conditions, the DMM returns the measurement’s absolute value so as to prevent

confusion associated with negative readings. The Hantek HDM Series DMMs will return negative

values. This allows the most accurate results after a NULL operation.