Spektrum SPM9548 - Manual (Page 8)

EN
RPM (optional sensors, sold separately)
Two RPM sensors are available: SPMA9569 for nitro and gas engines, SPMA9558 for
brushless electric motors.
Engine RPM Sensor
The optional engine RPM sensor mounts inside the backplate of aircraft engines. The
sensor picks up the crankpin as the engine rotates giving accurate RPM. Additionally,
you can use this sensor as an RPM pickup on any rotating gear/collar or shaft that
has a steel setscrew or other magnetic metal by locating the sensor within 5mm of the
rotating steel object.
Note: On some engines you may need to space the sensor further away from the
backplate. The sensor picks up the crankpin only; on some engines if the sensor
is too close, it will not distinguish the crankpin from the crank weight.
Installation
Install the backplate sensor in the backplate referring to the photo above.
Install the connector into the RPM port in the TM1000.
Testing
Turn the transmitter and receiver on and scroll to the RPM telemetry screen.
Rotate the engine rapidly and the RPM should register on the screen.
The RED LED on the TM1000 indicates the sensor is picking up properly.
You may need to adjust the sensor’s position to optimize the pickup. Move the sensor
closer or farther away until you have a reliable RPM pickup.