Marshall Instruments specializes in OEM, custom and private label electronic programmable speedometers. Contact us today for a quote.
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Signal
Marshall speedometers work with signals from both hall effect and magnetic pickup (i.e. vehicle speed sensors) sensors. Any speed sender or electronic module that meets the following two conditions can be used with our speedometer:
- Pulse range generated proportional to the vehicle speed
- Output within the voltage ranges listed below:
- 3.0V peak (Square Wave) or greater, typical for 3 wire hall effect sender outputs
- 3.0V peak to peak (Sine Wave) or greater, typical for 2 wire vehicle speed sensor outputs
If you currently have a mechanical speedo (cable driven) you will need a GM or Ford hall effect sender.
Calibration (Pulses per Mile)
Pulses per mile (PPM) is the number of pulses that the speedometer
receives for one (1) mile driven. The speedometer needs to know
this information to accurately indicate speed. Marshall electronic programmable speedometers accept a very wide range of PPM (4,000
to 200,000 PPM). This is very convenient when making changes to
differential gear ratios and tire sizes. Just recalibrate the
speedometer whenever changes are made and the speedometer will
automatically adjust for the changes and accurately indicate speed. Marshall speedometers come calibrated for 16,000 pulses per mile.
To calibrate:
- With the ignition off, press and hold the CALIBRATION/TRIP
button.
- Turn the ignition on, then release the CALIBRATION/TRIP
button.
- The odometer/trip display will indicate CAL to verify that
calibration mode has been accessed. The pointer will move to 50% scale.
- Drive the vehicle EXACTLY one (1) measured mile then stop.
- Press the CALIBRATION/TRIP button again to complete the
calibration.
- If the number of PPR is between 4,000 to 200,000 the
odometer/trip display will indicate the actual pulses counted by
the speedometer for five (5) seconds. This indicates a
successful calibration.
- If the number of PPR is below 4,000 at the end of one mile, the
odometer/trip display will flash for five (5) seconds
after the button is pressed. The calibration will not be updated,
and the original calibration will be maintained. Correct the
problem and recalibrate the speedometer.
- If the number of PPR is above 200,000 at the end of one mile,
the odometer/trip display will flash for five (5) seconds
after the button is pressed. The calibration will not be updated,
and the original calibration will be maintained. Correct the
problem and recalibrate the speedometer.
Operation
Marshall speedometers have a digital odometer and 2
separate trip odometers (TRIP 1 & TRIP 2) that can be individually
reset. Interfacing with the speedometer is done through the
CALIBRATION/TRIP button.
- The speedometer will always display the odometer at power-up.
- Momentarily press the CALIBRATION/TRIP button once to
display TRIP 1, which will be displayed until the speedometer is
powered down or the CALIBRATION/TRIP button is pressed
again.
- Momentarily press the CALIBRATION/TRIP button a second
time to display TRIP 2, which will be displayed until the
speedometer is powered down or the CALIBRATION/TRIP
button is pressed again.
- Momentarily press the CALIBRATION/TRIP button a third
time to return to the odometer display.
- The speedometer will retain the TRIP 1 & TRIP 2 values even
when powered down.
- To clear TRIP 1 or TRIP 2, momentarily press the
CALIBRATION/TRIP button until the desired TRIP is
displayed, then press and hold the CALIBRATION/TRIP
button for approximately 3 seconds until the TRIP resets to 0.
Troubleshooting
My speedometer does not respond at all, what do I do?
Check all of the wiring connections and power to the
speedometer.
1. If the speedometer needle goes to zero when powered up,
but does not respond when the vehicle is at speed, there
is no signal to the green wire. Check to ensure that the
green wire is hooked to the proper location for a valid
signal.
2. If the speedometer needle does not go to zero when
powered up, the speedometer is not grounded properly or
does not have power to the (RED) wire. Check to ensure
a good chassis ground. Verify that the (RED) wire has a
12VDC supply.
My speedometer does not read correctly, what do I do?
Recalibrate the speedometer. Be sure that you are driving exactly one (1) mile. The speedometer calibration accuracy is dependent upon
driving exactly one (1) mile. Spinning the tires will skew calibration and the
speedometer will not be accurate.
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