Electronic tension gauge

Looking for ideas to measure tension on a steel cable. There are manual gauges that do this by measuring deflection, and I am trying to find a way to do something similar using a setup that could be connected to an Arduino.

See http://loosnaples.com/how-tos/tension-gauges

The gauges are used to measure tension of the rigging on a sailboat, to "tune" the mast by making adjustments with turnbuckles.

tibtib: Looking for ideas to measure tension on a steel cable. There are manual gauges that do this by measuring deflection, and I am trying to find a way to do something similar using a setup that could be connected to an Arduino.

See http://loosnaples.com/how-tos/tension-gauges

The gauges are used to measure tension of the rigging on a sailboat, to "tune" the mast by making adjustments with turnbuckles.

The only way anything can be connected to the Arduino is if it has some sort of communication ability such as Wifi, Ethernet, serial, SPI, I2C. I may have left something out.

Have you thought about measuring the resonant frequency?

You could perhaps use strain gauge or some kind of pizeo sensor connected to an analog input.

The arduino could measure the frequency, or easier the period. The shorter the period, the higher the tension.

Regards

Gareth

Yes, but two cables of different lengths or thicknesses will have different frequencies for the same tension.

I would go for some kind of strain gauge technique - deflect the cable by a known distance and measure the strain in your deflection tool to find out how much force it took to deflect it that far.

If you have access to the ends of the cable then you install a simple tension strain gauge inline with the cable.

ieee488: The only way anything can be connected to the Arduino is if it has some sort of communication ability such as Wifi, Ethernet, serial, SPI, I2C. I may have left something out.

I was expecting to use an analog input on the Arduino, perhaps having something that would change resistance as the strain changed. Results could be shown on an lcd display.

The sensor unit would have to clip onto the shroud (cable); there is no practical way to have an additional cable parallel with the one being measured.

I'd build something similar to this: http://www.abqindustrial.net/store/cbm-cable-tension-meter-cablebull-p-631.html. Replace the center wheel with a standard beam load cell, laying on its side, and with some type of appropriate roller or pad between the load cell and the cable -- a piece of Delrin would probably be fine.

You'll notice the left wheel is on an eccentric. When using the device it should be "open" then rotated to tighten down on the wire until a starting pressure on the load cell is reached, then it should be rotated an additional "X" degrees for tension measurement. That process will give a fixed amount of deflection of the cable while negating cable thickness.

Don't be put off by the price of the load cell above as they can be found in much cheaper versions. To interface between a load cell and the Arduino you'll need to get an appropriate amplifier. An HX711 module (~$3) is the best option available for price and accuracy.

That has given me a couple of ideas to try, along the lines of those tension gauges. Hopefully I can find a way to make an inexpensive version with an analog output! I want to add this capability to an existing application, which is used for two nearly-identical sailboats to sail together and "tune" their rigging by comparing performance changes. I am already using Arduinos on board but am looking to compare additional variables such as shroud tension.

Any force/pressure/tension measurement you do is going to require some form of strain gauge that will require an instrumentation amplifier (like the HX711) since strain gauges output values in the millivolt range (+/- ~20mv). Since you mentioned "analog output" you might be looking at things like force sensitive resistors but I'll warn you that those are not accurate enough for this type of task. If on the other hand you meant you wanted the sensor to output analog to other devices on the boat's network that would be a bad idea as well; sending analog over long wires leads to a lot of interference. Some type of digital protocol should be used.

It's an interesting project, and given the pricing of the strain gauges you linked it seems like there's a good opportunity there to make and sell something better.

I had envisioned something similar to those analog strain gauges, but replacing the readout with a sensor that would change resistance. I now see that it isn't practical to do that, and need to learn more about instrumentation, etc. if I am going to go ahead with this project. I'm not looking for any kind of analog output, but want to provide additional information to the Arduino that is already reading and processing other information.

The strain gauges that are available are expensive, but not something that your average sailboat owner would purchase. They are usually used when rigging is replaced or the mast is removed and then reinstalled.