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Here's some
old data I took back in 2001 on new (?) meters:
Volt (fuel)
meter
The following is a table of needle reading and measured voltage for a gauge in correct working condition. 'E' stands for empty, green is normal operating condition, with 'F' standing for full and white is charge only range. The numbers are when the needle splits the line between colors. Needle just moves 19.8V Bottom of red 26.7V Top of red, bottom of green, "E" 33.1V Top of green, bottom of white, "F" 39.0V Top of white, bottom of upper red, 45.5V Top or upper red 47.3V
Current (load) meter:
Shunt resistance is .000658 ohms, or 20" of #6 copper. Bottom of green = 0 mV. (0 amps) Top of green, bottom of yellow = 36 mV (55 amps) Top of yellow,bottom of red = 64 mV (97 amps) Top of red, = 90 mV (137 amps)
So your 100 mV guess was pretty close; they probably used one and then printed the scale a bit off.
Larry Elie -----Original Message----- From: SteveS [mailto:ssawtelle fcc net] Sent: Thursday, August 21, 2003 7:37 AM To: elec-trak cosmos phy tufts edu Subject: Re: (ET) Amp draw Don't think I've seen a reply on this so I'll give you my best
shot.
From measurements I've taken, I believe the meter (at least on
E12S) is 150A full scale. I think it's also a 100mV meter, so the shunt in the
tractor is .1V / 150A = 0.67mOhms. This squares pretty well with the resistance
of the 20" 6AWG wire used as a shunt in many models: .41Ohms/1000ft /1000/
12"/ft * 20" = 0.68mOhms
So you can use a 100mV meter movement or your DVM on the mV
scale and scale up using 100mV = 150A.
Data logging on my E12S while mowing has shown a few spikes up
near 100A, but the average is well below that.
Hope that's what you are looking for...
SteveS
E20
E12S
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