Pulse to Ma conversion to show a percentage open

I have a hydraulic motor mounted on a horizontal plate with an output shaft that has a bevel gear. The other end of the shaft protrudes from the non-drive end of the hydraulic motor enough to get a sensor to count or measure. The bevel gear meshes into another gear at right angles, with a larger diameter bevel gear and this shaft rotates to open and close a valve. The ratio is never 1.1 and can vary on every application. I would like to be able to display the position of the valve on a digital display showing the % open from 0-100. I was looking at a pulse (inductive sensor) to analog converter to enable the 4-20mA to be scaled, however when the valve shaft travels in the opposite direction the converter wouldn’t know. I am looking for a solution that requires 12 or 24VDc supply.

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Hi David.

What do you mean by “The ratio is never 1.1 and can vary on every application”? Does this mean that the same motor will be meshed with various size gears, so the rotational position of the motor can’t be used to determine the valve state?

The hydraulic motor can turn clockwise and anticlockwise to open a gate valve. Different valve sizes require a greater or lesser number of turns to go from fully open to fully closed. The bevel gear on the hydraulic motor is a fixed diameter, however the bevil gear it meshes to on the valve can be much larger depending on the size of the valve. If both bevel gears were the same diameter one turn of the hydraulic motot would produce 1 turn of the valve spindle. 1.1

Thanks for the clarification. I’m not well-versed on valves, but I’ve reached out to someone here at DK who I think may have some ideas. I’ll let you know what he comes back with.

Hi again David.

I just heard back. Our product manager that works with this type of equipment couldn’t come up with anything off the shelf that will be able to measure the valve position on the motor side when the valve gear could be different sizes. He’s thinking some type of custom device that require calibration for each application would be the only option. Sorry I can’t offer you anything orderable to solve the problem.

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Hello @davidhawthorn ,
Thanks for your inquiry. Below are a few example sensors and encoders we offer to provide some ideas to help get started with this custom build:

Proximity Sensors - Industrial

Encoders - Industrial

Hello @davidhawthorn,

What are you using to digitally display the percentage? Your solution might lie in the software you’re using. You mention that the shaft protrudes from the non-drive end of the hydraulic motor - what is the diameter of this shaft? If you use a tachometer to read the voltage,in which it will typically read positive voltage in one direction and negative voltage in the other; you may be able to scale that voltage to either increment or decrement a variable. If you know the ratio of the gears, you can include that in the scaling function, allowing you to easily switch the gears out with minimal changes to your scaling function.

Hi Klint
Currently I am looking at using a shaft encoder and then a remote display. We don’t have a PLC and are hoping the the panel meter can be programmed to display an indication like a pressure gauge showing 0-100% open or closed. I don’t mind what protocol is used between the shaft encoder and the display as long as it indicates the exact position.
Key is the voltage for meter,encoder and any other items is 12Vdc and they have an IP rating of IP56 minimum.

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@davidhawthorn,

Unfortunately I don’t believe that Digi-Key is going to carry what you need at this time. As you explore options, however, I do suggest abstracting everything as much as possible in order to ensure that your readings are accurate. The conversion of voltage to percentage implies that there will be a scaler equation used at some point (whether it be through an intermediate device or the display itself)- if you include the ratio of gears as an adjustable variable in the equation then the issue of changing out the gears should be negligible. I wish you luck on finding the solution to this project; if you’re able to find everything you need get it working please feel welcome to post your results. I personally think it is a very interesting project and would love to see it!

Regards,
Klint