Hello,

I'm having an issue with the amplifier (Alpine MRD-M605) amplifier that reads 0.4v less than true voltage.

Measuring with a DMM:
Car off at battery: 12.82V
Car off at amplifier terminals: 12.79V
ACC on at battery: 12.62V
ACC on at amplifier terminals: 12.59V
ACC on at amplifier readout: 12.2V
Car on, hot at battery: 13.8V
Car on, hot at amplifier terminals: 13.78V
Car on, hot at amplifer readout: 13.4V

The charging system is fine. Starts off at 14.3V volts and drops down to a steady 13.7-13.8V when the battery is topped up. The car is also running the big 3.

I've looked at the amplifier itself and there is no calibration options for voltage reading.

The ground itself has no issues as the amplifier is basically getting true battery voltage at the terminals (12.82 @ batt / 12.79 @ amplifier terminals). I thought maybe the amplifier is metering the voltage from the REM wire so I jumped the 12V+ to the REM terminal but no change. It is still reading 0.4 down from what the true battery voltage is.

Any ideas on why the amplifier is doing this? The amplifier runs fine and has no issues.

I'd appreciate any insight on this. Thank you.

 

tolerance variances in the parts used? Voltage reading might be taken internally after some power is used or after internal resistance causes some voltage drop? Inaccurately calibrated voltmeter in amp or your voltmeter? My guess would be the the voltmeter in the amp is just not as accurate as your handheld given it's really only a gimmick (bells and whistles).

 

Whether it's "bells and whistles", I'm not so sure. Techically the voltage is not metered correctly but in all situations the amplifier is exactly 0.4V down from the DMM. So there is some truth to what it's saying, just with a -0.4V offset.

 

Yep, looks like the amp is calibrated a little low.

 

Or the amp is calibrated a little low AND the meter is a little high so both could be within tolerance. Your not playing with lab quality equipment here and if you happen to compare 2 devices that vary in opposite directions, the will appear unreasonable.

 

why is this bothering you so much? mayb it is the dvm that is off? So, if you confirm that amp is reading less.. what then?

 

your only solution would be to open the amp and test the joints that the onboard meter is reading from. there may be resistance in between the terminals and where the meter may solder on the amp. but its probably just calibrated off a bit. i wouldnt be suprised if you open the amp and find a calibration screw somewhere.