PVREL w. MC012

[CShultz]

We have been using Danfoss PVREL Joysticks for many years to direct drive Danfoss PVG/PVE valves without the need for Plus+1/MC012-110 for instance.  The client has now had us use PVREL joysticks to drive PWM coils on pilot valves.  This requires a signal conversion of some degree between the PVREL and the PWM coils(we choose MC012-110).  However, bringing a PVREL signal into an MC012 input, the input is not linear so scaling the ratiometric signal has been very troublesome.  A 12v to a 24v system for example requires us to manipulate the program quite a bit and the output to one PWM coil is usually a broader range than the other.  IE - the signal is very progressive.  Is there a 'simple' way to linearize the input signal?
PVREL Data Sheet:
Input- 11-30uDC
Current Consumption: <80mA
Output Voltage: 25%-50%-75% (again, these are plug and play with PVEs)
Output Signal: Max. Load - Two Parallel Connected PVEs
Output Signal: Min. Load impedance to 0,5-Udc - 6 k?

I am to assume the last piece of data has something to do with my issue but I am far from an electrical engineer to know what that means :-)

[G30RG3]

I'm baffled you say the signal isn't linear.
As far as I know, the signal is close to 100% linear.
There is no deadband on the neutral position, and doesn't even have the capability to limit the max signal (as with the PVRES).
The 6 kOhm impedance is to ensure the load necessary to make sure the internal amplifier in the joystick stays within range, but as far as I know the joysticks work with MOhm range impedance without issue, in most cases.
In my limited experience these joysticks start working with a Udc voltage of 4.75V, (I've  so the 11 to 30 Vdc is rather conservative, but they're quite sensitive to ripple.  Are you sure the supply is stable? In an automotive application, I've even used the 155U2602 to replace an inching pedal (because that was all I had available at that moment) and fed it with the 5V sensor supply.
Watch out for wetting current issues.

[CShultz]

Thanks G3ORG3 for your input;
If I measure the PVREL signal on a benchtop multimeter (I dont have a scope) its as linear as it needs to be.
Of course, plugging it into a PVE directly, it works flawlessly.  We are using the PVREL w. NSS so in neutral the power is off, so technically there is a minor deadband but when pluggig it into the PVE it isn't noticeable.  I figured it would be a very simple thing to do :-) but it proved not to be.
When kicking out of the neutral safety switch, lets say it jumps up to 6.4vdc.. that will actually trigger the output on the other side of 50%.  I have used the service tool to create look-up tables to make adjustments which gets me by but one side of center has more resolution than the other.  Going to 24v changes the values entirely. 
I hope to work on it today and maybe the scope on the P1 ST will show the curve.

[G30RG3]

If the NPS is causing you this issue, and you find the jump in signal bothersome to the extent you need to go outside this dead-band to use the Joystick, I would recommend to use the function block Inputs Library / 3-point sensor. This will handle most, if not all your re-scaling and dead band issues, but you'll need to add some logic in front to translate the missing signal when the joystick output is 0 due to the NPS.
You could replace the input voltage signal with a "Snsr Pwr" voltage / 2" if the signal is below 5% , but once the voltage is within the 20-80% range routing the real input voltage to the block. That way, you'll lose the short circuit error handling so you'll need to figure out if that is an issue, and act accordingly.

[acmall]

I don't use the PVREL so I don't know if this will work, I am just looking at the schematic in the data sheet which may be simplified. From the schematic it looks like it could be possible to connect the neutral switch in reverse to have the output signal constant, that is connect positive supply to the the terminal that is normally the output of the neutral switch (+ with circle). The terminal that is normally the positive supply could then be connected to a digital input on the MC012 which could be used to disable the output when in neutral.

Of course this also depends on your safety requirements.