CALIBRATION OF THE MS8209 digital muLtimeter

DISASSEMBLY: Remove the two Philips-head screws from the bottom of the case and carefully lift the back off, bottom (screw holes) first.

NOTE 1: Test leads should be initially inserted into the COM (black) and VWHz (red) jacks.

NOTE 2: An alternative to any of these procedures is to adjust the variable resistors to match the readings of a known instrument under the same conditions.

NOTE 3: These procedures require experience in electronics alignment. Any damage resulting from attempting to calibrate this instrument will void the warranty of return and/or repair.

1. DC VOLTAGE ADJUSTMENT:

(1) Set the rotary switch to the  V AUTO range position.

(2) Connect the test leads to a known DC voltage less than 200 mV. Adjust variable resistor VR1 to read correctly on the LCD display.

(3) Confirm the adjustment by stepping the RANGE button through its other settings, noting the readings.

2. AC VOLTAGE ADJUSTMENT:

(1) With the rotary switch still in the  V range position, press the FUNC. button to select AUTO AC measurement.

(2) Connect the test leads to a known AC voltage less than 2 V @ 60Hz. Adjust variable resistor VR2 to read correctly on the LCD display.

(3) Confirm the adjustment by connecting the test leads to standard AC line voltage and reading the display.

3. DC CURRENT ADJUSTMENT:

(1) Set the rotary switch to the  400mA position.

(2) Unplug and reconnect the red test lead into the mA°C jack.

(3) Insert the test leads in line in line with a known DC current near 10mA and adjust variable resistor VR3 to read correctly on the LCD display.

(4) Confirm the adjustment by connecting the test leads to a known higher current of less than 400 mA and reading the display.

4. CAPACITANCE ADJUSTMENT:

  (1) Remove both test leads from their jacks. 

  (2) Set the rotary switch to the W position.

(3) Press the FUNC. button to enter the AUTO nF measurement.

(4) Insert a standard capacitance near 100 nF into the COM and VWHz jacks.

(5) Adjust the variable resistor VR4 to read correctly on the LCD display.

(6)Confirm the adjustment by substituting a higher standard capacitance and reading the display.

5. TEMPERATURE ADJUSTMENT:

  (1) Allow the instrument several minutes to stabilize in the test environment.

(2) Insert the test leads back into the COM and mA°C jacks.

(3) Set the rotary switch to the 0.1° C position.

(4) To adjust the normal indoor temperature (20° C), connect the test leads to a standard 0.798 mV DC source and adjust the variable resistor VR5 to read 020.0 on the LCD display.

(5) Set the rotary switch to the 1°C position.

(6) To adjust the high temperature (400° C), connect the test leads to a standard DCV 16.40mV source and adjust the variable resistor VR6 to read 0420 on the LCD display.

(7) Refer to the following chart for voltages vs. temperature; if they do not conform, repeat steps (4) and (6).

 6. HUMIDITY ADJUSTMENT:

  (1) Allow the instrument several minutes to stabilize in the test environment.

(2) Set the rotary switch to the %RH position.

(3) To adjust low humidity, place the meter in a test box set to 50%RH and adjust the variable resistor VR11 to read 050.0 on the LCD display.

(4) To adjust high humidity, place the meter in a test box set to 90%RH and adjust the variable resistor VR10 to read 090.0 on the LCD display.

(5) Repeat steps (3) and (4) if necessary to conform accurately.

7. SOUND LEVEL (dB) ADJUSTMENT:

(1) Set the rotary switch to the dB position.

(2) To adjust the low sound level (dB), place the meter in a test box set to 60 dB and adjust the variable resistor VR13 to read 060.0 on the LCD display.

(3) To adjust the high sound level (dB), place the meter in a test box set to 90 dB and adjust the variable resistor VR12 to read 090.0 on the LCD display.

(4) Repeat steps two and step three if necessary to conform accurately.

8. ILLUMINANCE (Lux) ADJUSTMENT:

(1) Set the rotary switch to the Lux position.

(2) Place the meter in a test box set at 1000Lux and adjust the variable resistor VR8 to read 1000 on the LCD display.

(3) Set the rotary switch to the X10Lux range position and adjust the variable resistor VR9 to read 0100 on the LCD display. This is a very “touchy” adjustment and may have to be repeated.

(4) Repeat steps two and step three if necessary to conform accurately.

NOTE: The 10A, Hz, resistance and diode ranges do not need adjustment.