Vega EMS-1 Operating Manual
Page 52
11.2.1 Extending the leads of thermocouple probes
Thermocouple leads as used with the EGT and CHT probes can be extended either with ordinary copper cable or with
special K-Type extension cable. The choice of either depends on your desired accuracy. If it is possible in your installation
to ensure that both ends of a copper extension cable will be at the same temperature (or very close), then it is quite
possible to use the copper cable. In most open-air installations this will be the case. Should this not be possible or you
require best possible accuracy at all times, you can obtain a special K-type extension cable. This cable is made from the
same metals as your probes cable and uses ordinary plastic sleeving as insulation. In either case, ensure that the cable is
not routed close to sources of electromagnetic interference of any kind. The voltages present in this cable are very small
and are subject to changes applied by external fields. This can lead to false temperature indications. You can check your
installation by using a hand-held transmitter, such as an air band radio. If you transmit a signal, no change in temperature
reading should occur.
11.2.2 Notes on thermocouple connections using the supplied harness
For maximum accuracy of the thermocouple temperature measurement, please ensure that either end of the harness
cable (where used for thermocouple probes) is at fairly even temperature (minimise the temperature difference between
the connector side of the cable and the side where you connect the thermocouple). If required, shorten the cable to fulfil
this need.
11.3 RPM Installation
The RPM 1 input is quite universal. The RPM 1 input can be used with signals from about 5Vpp to as much as 100Vpp.
The input is also AC coupled for easy installation. A noise filter is included that results in the input ignoring any high
frequency noise signals as long as this is below the detection threshold of about 2.5Vpp (Please see dipswitch settings
below)
The input impedance of the rev counter input is approximately 10Kohm. You can use series resistors as well as load
resistors for applications that have unusual signals.
The RPM 2 input is intended as a Rotor input or a RPM input from sensors that can output a TTL signal. A noise filter is
included that results in the input ignoring any noise signals as long as this is below the detection threshold of about 1.5V.
(Please see dipswitch settings below). The required input voltage swing must be less than 1.5V to more than 3.5V.
The 220Ohm ballast resistor can be connected across the RPM input to ground to reduce noise or secondary pulses on
the RPM line (This is often used with Rotax engines). The ballast resistor must not be inserted for direct magneto pickups
as the magneto pulse may have low energy in particular at idle.
After you have connected the RPM input terminals to the signal sources you will need to set the number of pulses per
revolution under the “RPM SETUP” menus. The calibration itself depends on your engine and rotor type and what kind of
signal you are using.
Installation of the EMS-1 is quite straight forward in most cases. The drawing in section 10.1 shows a typical EMS-1
installation. Please see the engine RPM connection guide for connecting popular engine types to the EMS-1.
11.3.1 Adjusting RPM sensitivity (RPM 1 Input only)
The EMS-1 has a sensitivity adjustment trimmer at the rear of the instrument. Adjust this trimmer using a small
screwdriver such that you get stable RPM readings over the entire RPM band of your engine. If your sensitivity is too
high, you may get unstable RPM readings (usually at higher RPM as electrical noise in the ignition system increases). If
the sensitivity is too low the RPM reading may remain at zero. Fully clockwise = maximum sensitivity.
Note: Always install EGT probes starting on Channel 1 followed by the CHT
probes without skipping any channels in between.
