Reply To: Bizarre eTape Sensor Behaviour

Hi James,

If its the standard variable resistance then you should be able to just use the switched 3V. The ADS1115 is going to be more accurate.

FYI in case its of interest, I did some work with it and here is what I found out about the  eTape;  as I remember with the eTape, was that in calibration it wouldn’t register to the printed zero mark – and had an “actuation depth”, maybe it has changed.   The general issue with an “elemental sensor” is that the raw sensing (in this case resistance) needs to be transformed into measurable units  – in this case mm or inches, and for the eTape it is non-linear.

https://milonetech.com/products/standard-etape

They have linearizing modules, 0-5V and 4-20mA  –  though it requires a 6-24V stimulation

I did try the 4-20mA version, but burnt it out as it didn’t have reverse protection voltage in it.

https://img1.wsimg.com/blobby/go/6e1bce17-f4fa-40c3-9d89-9bb7445697bb/downloads/4-20mA%20Module%20Data%20Sheet.pdf

Emails I sent, though maybe it has changed:

Subject: Configuring eTapes into a system?
Date: Thu, February 12, 2015 10:58 pm

Some issues coming up
1) ‘0’ depth marking on the eTape scaling can never relate to a 0
electronic reading.
The data sheet says Actuation Depth a nominal 1″ – it seems that most of
the eTapes start recoding pressure change at about 0.2″
So where does the linearity start and to how to design to meet it?
2) For the simple eTape interface circuits, do you have any recommended
formuleas/manufacturing algorithims that translate measured Vout to a
linear depth reading that can apply to any eTape received.
<div class=”moz-cite-prefix”>On 2/19/2015 10:23 AM, chris.milone@milonetech.com wrote:</div>

<div>Hi Neil,</div>
<div></div>
<div>Sorry for the delayed response.  Yes, a voltage divider output is a nonlinear function.  We are working with another customer who has written some Arduino code that he claims automatically linearizes the output but we haven’t been able to get this to work as of yet.</div>