TTI PL Series - Calibration - 5 V;7 A Module; Equipment Required; Preparation; Calibration

Calibration - 5V/7A Module
Equipment Required
A 5.5 digit multimeter with better than 0.1% accuracy on voltage and better than 0.2% accuracy
on current or use a precision current shunt.
A small switch, 560 Ohm resistor and a diode.
Preparation
Preset adjustments are located on both the main and driver pcbs. Presets are accessible from
both sides of the main pcb.
Take great care not to touch the mains connections on the transformers during adjustment. Use
an insulated trim tool. Allow five minutes warm-up before proceeding.
Calibration
To avoid errors when making voltage measurements the DVM must be connected directly to the
sense terminals.
Voltage - Differential Gain
Remove the link between + O/P and + sense only and fit a diode, cathode to + sense and anode
to + O/P. Connect the small switch across the diode. Connect the 560 Ohm resistor between
-O/P and + sense. Connect the DVM set to 20V range to the sense terminals.
Close the switch.
Set the DC output switch ON.
Set the output voltage to approximately 5V.
Note the reading
Open the switch and adjust VR4 on the main pcb for the same reading +/- 0.5mV.
Close and open the switch and check the reading.
Voltage - Output and Meter
Remove the switch and resistor and refit the link between + O/P and + sense.
Set the voltage control to maximum and adjust VR7 for 6.0V to 6.05V on the external voltmeter.
Note the reading and set the output switch to OFF, adjust VR8 on the main pcb for the same
reading on the internal meter.
Current
Set output switch to ON.
Set current limit control to maximum.
Set VR3 on the driver pcb fully clockwise.
Connect the DMM set to 20A range in series with an adjustable load to the O/P terminals.
Adjust the load for 5 to 6 Amp output current.
Adjust VR5 on the driver pcb so that the external and internal meters read the same.
Adjust the load and/or outputput voltage to give 7.1 Amps output current.
Fine adjust VR3 until the decimal points just start to flash. Check 7 Amps output can be achieved
without de decimal points flashing.
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