This page contains documentation and tips for installing a CalAmp LMU.

Note there are two models of LMU: the 2600 series and the 2700 series. The primary difference is that the 2700 series includes an internal battery that enables GPS reporting when external power is cut. Aside from the internal battery, the models are functionally equivalent.

Before installing an LMU, be sure to download and read the Installation Guide:

• LMU Hardware and Installation Guide

Note the information on this page is intended to supplement, not replace, the Installation Guide.

Tips:

• Install Label-side Up – The LMU should be installed label-side up for best GPS reception.
• Accelerometer Calibration – The LMU accelerometer detects excessive acceleration/braking as well as sharp cornering. The accelerometer is self-calibrating (generally within 3 minutes of power-up), so device installation orientation doesn't matter as long as the unit is mounted firmly.
• Minimum Connections – Page 14 of the Installation Guide shows the pinout for the connector and wire harness. At a minimum, you'll need to connect Power (pin 14), Ground (pin 15), and Ignition (pin 8).

Tips:

• Use Inputs 1, 3, or 4 For Most Equipment – For the inputs, note that Input 1 (pin 3), Input 3 (pin 6), and Input 4 (pin 7) work as you would normally expect - active is high (12V), inactive is low (0V), and the bias is low. Those inputs are good for equipment, such as PTO or Beacon, that is turned off most of the time.
• Input 2 Works the Opposite – Input 2 (pin 12) works in the electrically opposite manner - active is low (0V), inactive is high (12V), and the bias is high. That input is good for a switch or sensor that is normally turned on and should alert when turned off (grounded).

Terminology:

• Relay – A relay is an electrically operated switch. A relay enables a low-power signal (the LMU) to control a high-power signal (a high amperage and/or voltage circuit in a vehicle) while providing isolation between the two signals. Automotive grade relays are available at Radio Shack, auto parts stores, and the Internet.
• Open Collector – An open collector is a switched circuit that controls a connection to ground. Below is a schematic of an open collector. Open collectors are useful for Outputs because they are independent (within tolerance) of the voltage/current necessary to drive the Output.

Open Collector Schematic:

Tips:

• Always Use a Relay – Always use a relay to control an Output so that any problem or short in the main circuit (e.g. Common, Normally Open, or Normally Closed terminals) does not damage the LMU (negative coil terminal).
• Outputs 1 and 2 are Open Collectors – Page 45 of the Installation Guide shows the schematic for Outputs 1 and 2. To connect a relay:
  1. Connect the positive terminal of the relay coil to power (usually 12V).
  2. Connect the negative terminal of the relay coil to either Output 1 or 2 on the LMU.
  3. Connect the common terminal of the relay to power (usually 12V, but 24V on some trucks)
  4. Connect the normally open terminal of the relay to positive terminal of the equipment (e.g. beacon, horn, etc)
  5. Connect the negative terminal of the equipment to ground.

When the output is activated, the collector circuit inside the LMU will close and current will flow through the relay coil causing the relay to close (turn on). When the output is deactivated, the collector circuit inside the LMU will open and no current will flow through the relay coil causing the relay to open (turn off).

• Output 0 toggles 2V – Output 0 works differently. When activated, the signal is 2V. When deactivated, the signal is 0V. The problem is that most relays require 6V or more. To make use of the output, you'll probably need to add a transistor, opticoupler or some other switching mechanism to increase the voltage and drive a relay coil. Contact Ranger support before using Output 0.