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Digital Multimeter Calibration

 

Digital Multimeter is the electrical industry familiar device , all electrical technicians need this device. Digital Multimeter Calibration ensures correct operation instrument, currently many businesses are interesting.

1. Introduce Digital Multimeter

This device integrates many functions, making inspection, repair the electrical equipment more convenient and faster.

Digital Multimeter can also be applied in automatic measurement systems in the production of components and sell end-product in the electronics and auto industries…After fully programmed, the device will measure and send the measured parameters to the production system for real-time product quality control.

2. Digital Multimeter classification

Digital Multimeters are classified based on indication structure, convenience or accuracy.

2.1. Analog Multimeter

This type performs measurements such as voltage, resistance, Volt-Ohm-Milliam-Meter (VOM). Measurement results based on indicator needle. Low cost but not high accuracy, is gradually being replaced by electronic type.

2.2. Digital Multimeter – DMM

This type has measurement results displayed on a liquid crystal display. Compared with Analog, this type integrates more functions and wider scale, higher accuracy, and has more standards of anti-shock for the device. The price is higher. The device is compact but can check many parameters, so many electrical technicians are trusted. Currently, the digital multimeters calibration is also of interest to many businesses.

2.3. Pocket multimeter

This type has a compact design, pocketable, very convenient to carry, no power required. This type has higher accuracy than Analog type but lower than Digital type.

2.4. Precision Multimeter

Precision Mutimeter (Bench Multimeter) is a specialized type for measurement and calibration laboratories. High accuracy, for results up to 6 ½ digit. This instrument is applicable to complex measurement requirements.

3. Scope of procedure

Unit Under Test Characteristics Performance Range Performance method

DC Voltage

Up to 1.1 kV

Direct measurement to by a known DC Voltage

DC Current

Up to 20A

Direct measurement to by a known DC Current

AC Voltage

Up to 22 V 10 Hz to 1 MHz 22 V to 220 V 10 Hz to 300kHz 220 V to 1.1 kV 15 Hz to 1kHz

Direct measurement to by a known AC Voltage

AC Current

Up to 3 A
10 Hz to 10 kHz 3A to 20 A 45 Hz to 5 kHz

Direct measurement to by a known DC Current

Resistance

Up to 330 MΩ

Direct measurement to by a known Resistance

Capacitance

Up to 110 mF

Direct measurement to by a known Capacitance

Frequency

10 Hz to 1.1 MHz

Compared to a Calibrator with known Frequency Response

Diode

Up to 10 V

Compared to a known DC Voltage

Temperature

Type K (-200 to 1372) ºC

Calibrator generates a signal for thermocouple simulation calibration.

4. Standard and supporting device

✔ Calibrator, accuracy better than 3 times Unit Under Test (UUT).

5. Environment conditions

– Temperature: (18 ÷ 28)°C

– Relative Humidity: (40 ÷ 60)%RH

6. Preparation

– Visually inspect the UUT for obvious damage that may affect accuracy and/or operation and note any observations.
– Technician must be familiar with calibration techniques and the operator manual of the UUT being calibrated.
– Connect TI and test equipment to appropriate power source. POWER ON and allow warm-up as required by the manufacturer.

7. Perform

7.1 DC Volts calibration

– For calibration of DC Volts function, calibration points will be perform at approximately 10%, 30%, 50%, and 95% of UUT range. Other test point from 0 to 100% UUT range can be done follow customer’s requirements.
– Connect UUT DC VOLTS terminals to Calibrator OUTPUT terminals, observing polarity.
– UUT setting switch to DC Voltage mode. Some UUT require the test leads be changed to different jacks for range changes.
– On the Calibrator set the desired output value, then press OPR/STBY switch to OPR and read UUT value when it is stable.
– Set Calibrator OPR/STBY switch to STBY.
– Repeat the above process to test each DC Voltage range of UUT.
– Disconnect UUT from Calibrator.

7.2 DC Current Calibration

– For calibration of DC Current function, calibration points will be perform at approximately 10% and 95% of UUT range. Other test point from 0 to 100% UUT range can be done follow customer’s requirements.
– Connect UUT DC Current terminals to Calibrator OUTPUT terminals, observing polarity.
– Perform the following steps, when calibrating UUT with current values up to 20 ADC.
• NOTE:
For current >3 A, must change the test lead to the 20A terminal on the Calibrator.
– UUT setting switch to DC Current mode and at range to be test. Some UUT require the test leads be changed to different jacks for range changes.
– On the Calibrator set the desired output value, then press OPR/STBY switch to OPR and read the value when it is stable.
– Set Calibrator OPR/STBY switch to STBY.
– Repeat the above process to test each DC Current range of UUT.
– Disconnect UUT from Calibrator.

7.3 AC Volts Calibration

– For calibration of AC Volts function, calibration points will be perform at approximately 10%, 30%, 50% and 95% of UUT range. Other test point from 0 to 100% UUT range can be done follow customer’s requirements.
– Connect UUT AC VOLTS terminals to Calibrator OUTPUT terminals.
– UUT setting switch to AC Voltage mode. Some UUT require the test leads be changed to different jacks for range changes.

– On the Calibrator set the desired output value at 45Hz, then press OPR/STBY switch to OPR and read UUT value when it is stable.
– Set Calibrator OPR/STBY switch to STBY.
– Repeat the above process to test each AC Voltage range of UUT at 400Hz.
– Disconnect UUT from Calibrator

7.4 AC Current Calibration

– For calibration of AC Current function, calibration points will be perform at approximately 10% and 95% of UUT range. Other test point from 0 to 100% UUT range can be done follow customer’s requirements.
– Perform the following steps, when calibrating UUT with current values up to 20 AAC :
– Connect UUT AC Current terminals to Calibrator OUTPUT terminals.
• NOTE:
For current >3 A, must change the test lead to the 20A terminal on the Calibrator.
– UUT setting switch to AC Current mode and at range to be test. Some UUT require the test leads be changed to different jacks for range changes.
– On the Calibrator set the desired output value at 45Hz, then press OPR/STBY switch to OPR and read the value when it is stable.
– Set Calibrator OPR/STBY switch to STBY.
– Repeat the above process to test each AC Current range of UUT.
– Disconnect UUT from Calibrator.

7.5 Resistance Calibration

– For calibration of Resistance function, calibration points will be perform at approximately 10%, 30%, 50% and 95% of UUT range. Other test point from 0 to 100% UUT range can be done follow customer’s requirements.
– Connect UUT OHMS terminals to Calibrator OUTPUT terminals.
– UUT setting switch to Resistance mode. Some UUT require the test leads be changed to different jacks for range changes.
– On the Calibrator set the desired output value, then press OPR/STBY switch to OPR and read the value when it is stable.
– Set Calibrator OPR/STBY switch to STBY.
– Repeat the above process to test each Resistance range of UUT.
– Disconnect UUT from Calibrator.


7.6 Capacitance Calibration

– For calibration of Capacitance function, calibration points will be perform at approximately 90% of UUT range. Other test point from min to max UUT range can be done follow customer’s requirements.
– Connect UUT terminals to Calibrator OUTPUT terminals, observing polarity.
– UUT setting switch to Capacitance mode.
• NOTE:
The output is continuously variable from 190 pF to 110 mF.
Specifications apply to both DC charge/discharge capacitance meters and AC LCR meters. The maximum allowable peak voltage is 3 V. The maximum allowable peak current is 150 mA, with an RMS limitation of 30 mA below 1.1 μF and 100 mA for 1.1 μF and above.
The maximum lead resistance for no additional error in 2-wire COMP mode is 10 Ω.
– On the Calibrator set the desired output value, then press OPR/STBY switch to OPR and read the value when it is stable.
– Set Calibrator OPR/STBY switch to STBY.
– Repeat the above process to test each Capacitance range of UUT.
– Disconnect UUT from Calibrator.

7.7 Frequency Calibration

– For calibration of Frequency function, calibration points will be perform at approximately min, 50% and max of UUT range. Other test point from min to max UUT range can be done follow customer’s requirements.
– Connect UUT AC VOLTS terminals to Calibrator OUTPUT terminals.
– UUT setting switch to ACV and choose Frequency Mode.
– On the Calibrator set the desired output value at 3V, then press OPR/STBY switch to OPR and read the value when it is stable.
– Set Calibrator OPR/STBY switch to STBY.
– Repeat the above process to test each point frequency of UUT.
– Disconnect UUT from Calibrator.

7.8 Diode Calibration

– For calibration of Diode function, calibration point will be perform at approximately 75% of UUT range.
– Connect UUT DC VOLTS terminals to Calibrator OUTPUT terminals, observing polarity.
– UUT setting switch to Diode mode.
– On the Calibrator set the desired output value, then press OPR/STBY switch to OPR and read the value when it is stable.
– Set Calibrator OPR/STBY switch to STBY.
– Disconnect UUT from Calibrator.

7.9 Temperature Calibration

– For calibration of Temperature function, calibration points will be perform at approximately min, 50% and max of UUT range. Other test point from min to max UUT range can be done follow customer’s requirements.
– Connect UUT DC VOLTS terminals to Calibrator OUTPUT terminals, observing polarity.
– UUT setting switch to Temperature mode.
– On the Calibrator select the thermocouple type K and enter the desired output value, then press OPR/STBY switch to OPR and read the value when it is stable.
– Set Calibrator OPR/STBY switch to STBY.
– Disconnect UUT from the Calibrator and secure all equipment

8. Tolerance

– Customer required tolerances are to be used for all calibrations unless otherwise noted.
– If the customer does not supply instrument tolerance then manufacturing specifications or other approved sources are to be used as the default tolerance.

Nguyen Thuy

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Published by
Nguyen Thuy
3 years ago

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