level transmitter resistive type

You can connect the res. level to transducer to make 4-20mA, then use that signal as an input to any type of programmable PLC with a analog input

Thanks for the comments, actually the res level is connected directly to Diesel engine control panel and not to any PLC. I'm not sure if there's a way that I can replace the res level as it always get damaged when fuel overflows. Can I use any 4-20mA level Tx and how?

What keep you away to open the panel and figure out where output from Level Sensor is connected? It is strange that you do not have a diagram. Or info about Manufacturer of ther Panel.

Multimeter + Power Source required for test if none of above. Tests need diagrams and the instruction.

Usually vehicular fuel tank level sensors are somewhat crude devices consisting of a float at the end of a lever which controls the position of a sliding arm on a rheostat. If the tank contains contaminated water it can shunt the resistive turns of the rheostat causing erronious readings.

There are manufacturers (Gems for one) that make level sensors consisting of a floating magnetic donut that moves vertically on a column which contains a series of reed switches. This type of level sensor is more suited for hostile liquid environments. The sensor has to be configured for the height of the tank.

Another type that would work well and is available with a 4-20ma output is a capacitive level sensor. It consists of a stainless steel rod centered in an open bottom stainless steel cylinder. The level of liquid in the cylinder changes the capacitance between the rod and the cylinder. This type works very well in hostile environments.

It seems that the problem is control panel itself.

How it works is Control panel delivers current to transmitter and measure voltage on the transmitter back. This current may be much more than 20 mA (legacy systems)!.

If this is the case, u can not use even reed switch based level transmitters(jeoconed told).

For exact solution you must do 3 measurements:

i-Short circuit current from control panel. Connect an ammeter directly transmitter inputs of panel and read current value.

ii-Open circuit voltage of input. Connect a voltmeter transmitter inputs of panel.

iii-Maximum resistance of transmitter. You can measure this via an ohmmeter connected to transmitter.

( transmitter must not be connected to panel during these measurements!)

While these parameters known, i can suggest a solution.

Thanks guys, all your comments were been very helpful getting understanding of installation with limited documentation and resources. I manage to get in contact with the Engine supplier and has confirmed that their controller requires modification in order to accept new level transmitter 4-20mA output as it is currently designed with their fuel sender level transmitter as float switch lever arm type with variable resistance depending on the depth of medium.