# I need 3VAC and 2.5kHz .... HOW???

Hey everyone.

Super new to the Arduino world. I have some background with PLC stuff and some understanding of circuits and general electronics. I am decent at programming as well.

Here at work I found an LVDT that was given to me for a project. Without buying a PLC, Signal Conditioner, Power supply, etc... I figured I would give an arduino a shot.

I have a data acquisition block I may use to gather the output data from the LVDT (unless I can do it on the Arduino...im assuming I can somehow). But right now, I am just trying to get the device power. The trick is it requires and AC input...

The LVDT is...
3VAC (P2P)
2.5kHz

Is there anyway for me to produce the required voltage / frequency to supply the sensor? If so, how?

You might be able to generate this sine wave with an Arduino but it won't be very clean and the performance (which you did not specify) of the LVDT will suffer.

It may be better to generate your own sine wave, do your own gain and limiting to 3 VAC (including removal of DC), and your own driver to drive the impedance of the LVDT. The impedance of this model of LVDT ranges from a low of 400 ohms to a high of 1950 ohms. I cannot read which dash number you have so YOU will have to decide what design impedance you should aim for.

(The image appears to show a -1000 model which has an impedance of 1650 ohms according to the data sheet, but I do not know if this is the real part.)

While it is challenging to generate a clean sine wave (you may want to use a narrow bandpass filter), you will get much better performance from the LVDT.

Good Luck!

vaj4088:
... and the performance (which you did not specify)...

Doesn't have to have amazing resolution. Right now this is more of a test / proof of concept anyway.

vaj4088:
It may be better to generate your own sine wave, do your own gain and limiting to 3 VAC (including removal of DC), and your own driver to drive the impedance of the LVDT. The impedance of this model of LVDT ranges from a low of 400 ohms to a high of 1950 ohms.

Ok, so how the heck would someone do that haha?

PancakeShake:
Doesn't have to have amazing resolution. Right now this is more of a test / proof of concept anyway.

Ok, so how the heck would someone do that haha?

If this is for a commercial application, you buy the signal conditioner from Macro Sensors instead of kludging up something you don't appear to know anything about.

ieee488:
If this is for a commercial application, you buy the signal conditioner from Macro Sensors instead of kludging up something you don't appear to know anything about.

We had 10 of these sensors in a trash can. They were pulled off an old machine and I asked to have them to attempt to implement in a test bench. Nothing to support production.

Go to your local 'Goodwill' store ,or wherever you can buy junked out electronics, and look for a small CRT monitor or Battery powered black/white analog tv. Rip it, locate the filament transformer. See if you can figure out how to knock down the 6.3Vac to ~~3Vac.

EDIT: oops, my bad, I forgot it had to be at 2.5KHz....

PancakeShake:
We had 10 of these sensors in a trash can. They were pulled off an old machine and I asked to have them to attempt to implement in a test bench. Nothing to support production.

commercial as in non-hobbyist context

Just because they came off an old machine does not make the parts any less demanding in its requirements.

Quick and dirty solution is to use high speed PWM and table-lookup to generate your 2.5kHz
sine wave at +/-2.5V by using a blocking capacitor. These devices seem to have a fair impedance,
so you may get away with 62.5kHz PWM (no prescaler, 8 bit PWM).

Sample the result differentially by tying one output to a 2.5V virtual ground and sampling the other
output (via 4k7 resistor for safety) at full rate and calculating rms voltage from mean. Determining
the sign of the result should be easy if you look at the samples at appropriate points of the output sine
loop.