THEORY OF OPERATION SORENSEN DCS SERIES MANUAL
3-8
3.2 Meter Circuit (A1 Assembly)
The A1 assembly is comprised of the voltmeter and ammeter displays, the output voltage and current limit
controls, the local operation OVP adjusting potentiometer and the indicator LEDs. The operation of the voltage
and current controls, the OVP potentiometer and the indicator LEDs is covered in the A2 description in Section
3.1. Refer to the schematic diagram in Section 6 for the following discussion.
3.2.1 Voltmeter
U2 is a 3 1/2 digit analog to digital converter which converts the analog input from the A2 board voltage control
circuit to a digital display on seven segment displays DS5-DS8 (maximum display is 1999). The 6.2V reference
from pin 5 of connector J1 is divided down by resistors R16 and R17 and potentiometer R18 to provide the
reference for the converter. The analog input from the voltage control circuit (via pin 6 of connector J1) is filtered
by resistor R9 and capacitor C14 before it is input to pin 31 of the converter. Capacitor C12 and resistor R7 set the
conversion frequency to approximately 3 times per second. Resistors R8, R11 and R12 are used to select the
appropriate decimal point position depending on the model of the power supply.
3.2.2 Current Meter
The current meter circuit operates in the same manner as the voltage meter circuit with U1 performing the
conversion for display on DS1-DS4. Capacitors C4 and C6 provide additional filtering on the meter analog input.
Resistors R2, R5 and R6 are used to select the appropriate decimal point.
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