GW Instek GOM-801H - Manual (Page 6)

GOM-801H DC MILLI-OHM METER
USER MANUAL
⎯ ⎯
6
Front Panel
1. Power Switch Power on/off switch.
2. Range 7 steps: 20, 200mΩ, 2, 20, 200Ω, 2 and 20kΩ.
3. HI/LO
Set the “SET/TEST” switch to “SET” position,
then select HI/LO for high or low value setting.
4. SET/TEST
This button can be used for testing or HI/LO
value setting.
5. FORCE Terminal “+” Test terminal.
6. SENSOR Terminal “+” Test terminal.
7. SENSOR Terminal “-” Test terminal.
8. FORCE Terminal “-” Test terminal.
9. HI of Comparator Set For high value setting.
10. LO of Comparator Set For low value setting.
11. Panel Meter To indicate the test value.
12. HI Indicator
This indicator will be lighted up when the test
value is higher than the setting of high value.
13. GO Indicator
This indicator will be lighted up when the test
value between high and low setting. The buzzer
will be sounded up 2~5 seconds when the GO
indicator is on.
14. LO Indicator
This indicator will be lighted up when the test
value is lower than the setting of low value.
GOM-801H DC MILLI-OHM METER
USER MANUAL
⎯ ⎯
7
5. CIRCUIT DESCRIPTION
z DVM Circuit
The DVM is an A/D converter by using IC U301.
z 10 or 100 Times Signal Amplifier
The signal amplifier uses IC U401.
z Test Range selected buttons
There are 7 steps of Test ranges to be selected. It will not affect its
accuracy due to the alternation or temperature.
z Constant Current Source
The circuit uses IC U201and U202 and transistors Q203 and Q204 to
produce constant current.
z Comparator Set and HI, GO and LO Indicators
The setting is consists of the resistors and the variable resistors. The
comparator use IC U403 and U404. The HI, GO and LO indictors use
transistors Q401~Q407.
z Voltage Regulator Circuit
The power supply has regulated output of ±5V and ±15V voltage, which
are regulated by using Q201, Q202 and Q301 resistors to control D201,
D202 and D301 zener diodes. The +5V voltage regulator circuit uses IC
U302 voltage regulator.