Project Grey Mustang 5.0: Part 8 – Testing Auto Meter’s Elite Gauges

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Auto Meter’s Elite gauges don’t use the inexpensive single-wire senders that lower-tier gauges use.  Instead, they use multi-wire senders like OEMs do when installing sensors for an engine’s ECU. 

Pictured is the oil pressure sender.  You can see that it looks far more rugged than the bell-shaped ones that you get from the local big-box store.  It even has a serial number on it. 

This provides two benefits: first of all, these sensors are more accurate. Lower-end gauges that use a single-wire sender are purely analog.  These gauges generally work by measuring the resistance between the gauge and the engine’s ground.  The single wire is connected to the top of the sender, which is grounded to the block.  The internal resistance of the sender changes based on pressure or temperature, and the gauge acts as an ohmmeter.  This has quite a few problems in terms of accuracy: a poor block-to-chassis ground or noise from a poorly-insulated ignition system could cause inaccurate readings.

The back end of the Elite pressure sensor has three pins inside a weather-tight, OEM-quality connector.

However, the Elite gauges have a multi-wire setup.  In the case of the pressure sensor pictured above, the three wires are power to the sender, a dedicated ground, and a signal wire to send the reading back to the gauge.  The inclusion of a clean, dedicated ground eliminates problems caused by noise interference or high impedance caused by poor grounding of the sensor.  (In the telecomm industry, we call this an Isolated Ground.)  Having a separate power and signal wire also increases accuracy, because the gauge sends a very specific voltage (5 V) to the sender and receives an exact voltage back, as opposed to utilizing the 12-V alternator-supplied voltage which can vary wildly.

The second benefit to these higher-quality senders is that Auto Meter’s elite gauges can actually output a 5-volt signal for use as input into a data logger.  That’s right; using an Auto Meter Elite-series gauge allows you to use one sensor for both your gauge and your data logger.  This helps keep clutter and wiring to a minimum inside the engine bay.  There are two wires on that wiring harness for this purpose: the black wire should be connected to the ground pin on the data logger, and the yellow wire is the actual sender signal.

 

Parameter

Low Value

High Value

100-PSI Gauges

0 PSI = 0.5V

100 PSI = 4.5V

35- and 60-PSI Gauges

0 PSI = 0.5V

60 PSI =  4.5V

Temperature Gauges

60°F = 0.5V

340°F = 4.7V

This chart illustrates the data-logger output for various gauges.  Auto Meter makes several Elite boost gauges, as well.

Auto Meter is so concerned with making sure your data logger gets accurate data, they’ve individually calibrated each gauge.  On the back of the gauge is a reading that can be plugged into a provided formula that then provides exact voltages for each reading down to the millivolt (one-thousandth of a volt).  How’s that for accuracy?

That voltage (5.018 V) is plugged into a formula to give the exact voltage over the entire range of the sender’s operation.

Auto Meter also uses the highest quality components in the gauges themselves to guarantee the highest accuracy.  Instead of a simple analog ohmmeter setup, the Elite gauges use a digital stepper motor controlled by custom-printed circuit boards designed and manufactured in Auto Meter’s facilities.  The gauges also self-calibrate each time they are powered on.

So after drooling over the gauges and their features and benefits, I moved on to actually installing them into Project Mustang.  Thanks to the included wiring harness, the installation was extremely easy.  There were very few splices to be made, since everything just plugged right in.  The only splices actually made were power, illumination, and ground wires.  I didn’t have to worry about adding crimp-on terminals or anything to connect the sender.

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