I will get back yo you tomorrow. When I have verified that it will work.
What I have in mind is: if you look at the circuit diagram in the link:
http://www.lascarelectronics.com/data/pdf/SP%20400.pdf
By default the display is a VOLTMETER with a gain of 10.
This means that if there is a difference of 199.9mV between in_Hi and IN_Lo then it will show 1999. (After this you add the "." wherever you want)
So. We have 10mV that we want to show as 209 that is a gain of 20.9.
http://hallaweb.jlab.org/tech/jackja..._app_notes.pdf
From this site we get:
READING = 1000 * VIN / VREF
(Originally Vref is set to be 100mV and with the small calibration pot under the display you change this to 100mV if it is not exactly that)
And the circuit that creates this vref is:
V_PLUS--------(100K)------+----(3K)-----(1K POT)-----Vref_LO
VRef_HI is connected to where that + is.
PS:The editor deletes all white spaces so it is difficult to do ascii drawings.
So we want to set to half its value.
We will exclude the pot for now.
VRef_HI = 3/103 * V_PLUS
To get 1/2Vref we would Need to change the 100K resistor to a 203K resistor.
That resistor is R4, now I did not dare to remove the backlight from the display. But if you have an ohmmeter then you should be able to tell which one it is. The circuit diagram does not show any other 100K's. Just one other 130K for the battery indicator light. If you follow from the pot then first you will find a 3K then a 100K resistor.
Where did you get the lascar from? And how is it used in its original configuration? How did it die? I know they do not like pressure or water.
Teoman