8 tips to teach you how to use a multimeter correctly

3. Selecting the appropriate range can speed up measurements because the auto-range feature can cause delays when you measure low-frequency signals.

4. To sample the waveform, the multimeter needs to determine the signal period. Use the ACBAND command to determine the pause value. If you do not use the ACBAND command, the multimeter may pause before the waveform repeats.

5. Synchronous sampling mode uses level triggering to synchronize the signal. However, noise on the input signal may cause false level triggering, resulting in inaccurate readings. It is important to select a level that provides a reliable trigger source. For example, avoid the peak of a sine wave because the signal changes slowly and noise can easily cause false triggering.

6. To get accurate readings, make sure your surroundings are electrically "quiet" and use shielded test leads. Enable level filtering, LFILTER ON, to reduce sensitivity to noise.

The 34401A can be configured in the same way as the 34410A and 34411A.

Uses analog circuitry with DC blocking capacitors to convert RMS voltages. It can measure signals as low as 3 Hz. For best results, select a low-frequency filter, use manual ranging, and verify that the various DC offsets are stable. When you use the slow filter, a 7 s delay is inserted to ensure that the multimeter is stable.

Tip 5: Selecting a sensor for temperature measurement with a digital multimeter

There are four common sensors used for temperature measurement in DMMs: Resistance Temperature Detectors

(RTD), thermistor, IC temperature sensing device and thermocouple. They each have their own advantages and disadvantages.

Tip 6: Use a thermistor for better sensitivity

Thermistors are made of semiconductor materials and offer high sensitivity, but they have a limited temperature range, typically -80°C to 150°C. The relationship between temperature and resistance of a thermistor is nonlinear, so the conversion algorithm is very complex. Agilent multimeters use standard Hart-

The Steinhart approximation provides an exact transformation with a typical resolution of 0.08°C.

Tip 7: Get better accuracy with RTDs

Resistance temperature detectors (RTDs) provide a very accurate and highly linear relationship between resistance and temperature over a temperature range of approximately -200°C to 500°C. Modern multimeters such as the Agilent 34410A provide temperature measurements of IEC 751 standard RTDs with a sensitivity of 0.0385 Ω/°C.

IC temperature sensing device produces a voltage that is linearly proportional to degrees Celsius

Many manufacturers offer probes that produce a voltage proportional to degrees Celsius or Fahrenheit. These probes typically use an IC temperature sensing device, such as the National Semiconductor LM135 series. These ICs cover a temperature range of -50°C to +150°C. You can easily calculate the temperature from the probe output displayed on the multimeter. For example, 270 mV is equivalent to 27°C.

Tip 8 Thermocouples for Extreme Temperature Measurements

Thermocouples can measure an extremely wide temperature range of -210°C to 1100°C, and their rugged construction can withstand harsh environments. Unlike other types of temperature sensing devices, thermocouples measure relative temperature, so they also require a reference junction for absolute temperature measurement. But for most applications, adding an external reference junction is not practical. We recommend using the Agilent 34970A data logger and the 34901A 20-channel multiplexer with built-in reference junction. The 34970A also has built-in temperature conversion algorithms for commonly used thermocouples.

summary

To monitor one temperature, a thermistor and a multimeter such as the 34410A are simple, low-cost solutions. To get accurate temperature readings, an RTD should be used. When monitoring multiple temperatures or high temperatures, a dedicated data logger is the best choice.