What input a general contact seeks

[skysailor]

I am finally beginning to wire the EMS module to the various sensors. I am curious as to how the units seeks it's information. For instance, in the oil pressure, oil temperature and fuel pressure inputs there is only one wire with the sender requiring a very good ground. It makes sense to me this wire is using the variable resistance of the sender to measure a voltage. When reading the trim sender install the MAC unit is used as an example. In this case 5V is applied to one end, ground to the other while the signal lead is tied to the EMS.

My question relates to two other senders I have. I bought a slide potentiometer which I installed to use for elvevator trim position due to the large amount of travel needed. It has two leads which are essentially the end of the resistor and the wiper. One end goes to the general contact input I assign for that sensor. I would think the other would go to the 5V line from the EMS. Is this correct? The other sender is a fluid level sensor. It has a wire for 5V, one for ground and one for the sensor. There is continuity between the 5V input and the sense wire when no fluid is present and none when no fluid is present. It seems I can wire it this way and define the sensor as a contact with 0-2V as one state and 3-5V the other.

 

[dynonsupport]

The EMS module always reads voltages. Eveything must be converted to a voltage to be measured.

For "single wire" senders, they are actually two wires, one between ground, which is connected to the EMS as well, and one to the input pin. These are usually (but not always) resistive senders, where they have a varying resistance to ground. This does not inherently make a voltage. To measure this resistance, there is a resistor inside the EMS module, hooked to the same pin, and also hooked to the internal 5V reference.

Thus you have a voltage divider, where there is a known resistance to 5V, a known voltage between the resistors, and an unknown resistance to ground. You can solve for that one unknown via the other knowns.

When you use something like a slide potentiometer and hook one end to ground and the other end to 5V, the output varies from 0V to 5V. This is easy as it's just a varying voltage.

With your elevtor trim potentiometer, you have a few options, but the easiest is to hook it up like any other pot. Hook one side to ground, one to the EMS 5V, and then the output to an EMS GP input. You can then calibrate this.

Your fluid sensor sounds a bit more problematic. I assume it is an "active" device and actually needs 5V, and has chips inside and is not just a simple mechanical switch?

If so, this is a bit of a challenge. The EMS pulls the inputs to 5V. Thus, with nothing connected, they read 5V. So if your switch either outputs 5V or nothing, the EMS will always read 5V. We have 4 inputs on the EMS that might be able to work with this output if you put a resistor to ground in the system. Check the way your switch works and get back to us and we can help you out.