V995's Voltmeter

[JonnyZero]

When checking against a calibrated Fluke 77III I have from work, the Bel reads .3 - .4V higher.

Has anyone noticed this? I know that the V995 is not a calibrated instrument but I had expected it to be in the +/- .1V range, for the feature to be meaningful.

[djrams80]

I don't know how accurate it really needs to be. If it reads 13.6 every day, then reads 11.4 one day, I'm sure the average user would get the point. Does it really matter if the baseline reading is 13.6 or 13.2?

[JonnyZero]

Well for one, at 80 degrees F, 12.80V with engine off indicates a fully charged battery. 12.40V is 50% charged.

.3V higher charging voltage could mean a bad voltage regulator and slowly frying your battery.

I was concerned with too high of charging voltage at first, then after shutting off the engine and removing the suface charge, the battery read consistantly over 13V, then I realized something was wrong and took my Fluke to it.

[focalcivic]

When checking against a calibrated Fluke 77III I have from work, the Bel reads .3 - .4V higher.

Has anyone noticed this? I know that the V995 is not a calibrated instrument but I had expected it to be in the +/- .1V range, for the feature to be meaningful.

I would assume the volt meter is for informational use only, say you turn the key to the on position and get 12. blank volts you know you will have enough juice to start the car. When the car is running at 14.blank volts then the average user will know the battery is most likely functioning properly. I would bet there are variances from unit to unit.

[jdong]

I'd expect a radar detector voltmeter to be accurate within +/- 1V so that it gives the user a rough idea of what shape their battery is in. I wouldn't expect it to even be within 0.1V precision. It is, after all, a radar detector and the voltage information is probably estimated from some input on their power supply with a cheap A-D converter pin that I doubt is sampled frequently.

[MEM-TEK]

I'd expect a radar detector voltmeter to be accurate within +/- 1V so that it gives the user a rough idea of what shape their battery is in. I wouldn't expect it to even be within 0.1V precision. It is, after all, a radar detector and the voltage information is probably estimated from some input on their power supply with a cheap A-D converter pin that I doubt is sampled frequently.

Naw, its not meant to give an accurately calibrated reading but merely a consistent reading for a couple of reasons. First, RDs generally only have some very small filtering capacitors and no chokes inside to moderately reduce alternator ripple rather than to completely eliminate it. Those filtering caps will push the voltage reading up very slightly. Second, the fuse in RD power cords causes a very small voltage drop. Third, most RDs are powered using extremely thin gauge stranded phone wire. All of this adds up to a non-calibrated reading for the voltage. My RD's displayed voltage doesn't exactly match what I measure with my volt meter, but at least my RD's voltage display is consistent in what it displays for my RD's hardwired power source.

At least your RD's voltage display can let you know roughly two weeks before your alternator completely dies. If your RD always displays 13.6V for example, and its voltage display begins to drop by a tiny amount each day, then that is a good sign that your alternator is getting weak and is near failure. Why? Because the ripple from the weak alternator is decreasing and the internal tiny caps within the RD are charging to a slightly lower peak voltage.

[ahmadr]

http://www.radardetector.net/viewtopic.php?t=28077

[JonnyZero]

I suppose I will hardwire my Fluke and suction cup it to the windshied too, between the GPS and the RD.
If I get stopped by a LEO, I can go, dude, I have got more stuff on my dash than you.