Wow, The transducer they sold you has a variable voltage output.
The gauge is looking for variable OHMs input.
The Smith Sender PN PTR1000-6-10 shown on all the sites I can find says it works with the Smiths
Oil press gauge PN APG1310-02C.
The Smiths sender Ohm range is 300-10 ohms.
https://www.smiths-instruments.co.uk...re-transducers
I'd contact Nissonger and request an explanation on how the gauge is going to covert the voltage to a usable reading. I may be missing something totally here but it doesn't feel like it. Whats also weird is the Nissonger site lists the PTR1000-6-10 sender.
I must admit the transducer is working since you do have a gauge scale reading, its just off quite a bit. So either the transducer is faulty or they sent you the wrong one I'm guessing.