DSE Q2220 3.5 digit LCD display HELP please?

[David]

One of the applications circuits on the paperwork that comes with this
device allows the measurement of the voltage of the supply powering it.
I've built it.

On the BOARD of the device itself are a number of pads, tracks and
connections that LOOK to me as if they are designed to do this job with
appropriate SMD components. I can't quite figure out whether this is the
case.

Has anyone used the back of the board to set up the negative power supply
generator as shown on the paperwork? Any advice/info?

Thanks

 

[JimW52]

One of the applications circuits on the paperwork that comes with this
device allows the measurement of the voltage of the supply powering it.
I've built it.

On the BOARD of the device itself are a number of pads, tracks and
connections that LOOK to me as if they are designed to do this job with
appropriate SMD components. I can't quite figure out whether this is the
case.

Has anyone used the back of the board to set up the negative power supply
generator as shown on the paperwork? Any advice/info?

Thanks

Although I haven't tried it, I have traced the tracks and it is indeed
the same as the schematic shown. Go ahead and build it, all should be fine.

Jim

 

[Colin Earl]

One of the applications circuits on the paperwork that comes with this
device allows the measurement of the voltage of the supply powering it.
I've built it.

On the BOARD of the device itself are a number of pads, tracks and
connections that LOOK to me as if they are designed to do this job with
appropriate SMD components. I can't quite figure out whether this is the
case.

Has anyone used the back of the board to set up the negative power supply
generator as shown on the paperwork? Any advice/info?

Thanks

Yes, the PCB allows adding the -ve supply generator components. From
memory there are also solder pads which need bridging and/or some PCB
links cut to join the measurement reference to the 0V supply terminal
and shift the module supply to the output of the added generator.

I remember also thinking a bit later that you could get the module to
measure its own supply just by using a 3-resistor voltage divider,
with the resistors chosen so that the voltage at the bottom of the
middle resistor was above whatever it needs to be, and the voltage
across the middle resistor was 1/10th the supply. Then set the range /
decimal point accordingly and just measure the voltage across the
middle resistor.