Calibrating a vacuum gauge to arduino

Hi everyone!! I need some suggestions in choosing a cheap vacuum gauge that can be calibrated based on the readings... My range is 0 to -60kPa. Please help

Please tell us more.

Do you only want a pressure (vacuum) sensor ?
Do you want to display it on a LCD display or on a gauge ?
What do you mean with calibrate ? If you buy a calibrated sensor, it that okay ?

I assume you mean relative pressure ? Relative to the surrounding baromic pressure.

Is it possible to place the sensor in the vacuum chamber and measure the absolute pressure ?

-60kPa = -0.6 bar = -8.7 psi
That is not a high vacuum.

Do you want something industrial ? something that can withstand high temperatures ?

The cheap BMP085 is very accurate. It is a baromic pressures sensor that starts at -70kPa. If you place one inside the vacuum chamber, and one outside, you can calculate the relative pressure.

Currently I just have a mechanical vacuum gauge but this doesnt help me in anyway to export the data what it reads to the arduino. I just wanted to display some sort of mapped value on the serial monitor of the arduino window. Please check this link http://forums.hackaday.com/viewtopic.php?f=5&t=2524&p=12205&hilit=vacuum+gauge#p12205 This is what I want exactly, need to display the readings externally as well as feed it to the arduino through the analog input pin, but I feel the digital gauge is too expensive for me . Is there a way to make this a lot cheaper ?

An ordinary automotive Manifold Absolute Pressure (MAP) sensor would give you an analog output signal which you could read via an analog input, but I don’t know whether you’d be satisfied with 10-bit resolution.

You want a carburetor sync ?

I don’t know if a digital pressure sensor is fast enough.
An analog sensor is easier to start with.

The Freescale MPX series are often used.
This projects uses MPXV5050V. The sensor uses 5V and the output can be connected an analog input of the Arduino.

You could use a display like these: http://www.adafruit.com/products/879

Ya something like a carburetor sync I'm making a flexible concave mirror.. Your idea seems cool.. Thank you so much :slight_smile: :slight_smile:

So you are not using a motor bike or car or engine ?

When using a flexible concave mirror, the vibration of the motor could be passed on to the membrane. If you use a vacuum chamber and perhaps a damper in the vacuum tube near the motor you can avoid that.

When using a vaccuum chamber, it is still possible to use those very accurate BMP085.
They can be set to high resolution, and if you use the average of 10 high resolution samples, the accuracy is even better. They are already calibrated when you buy them, even if you buy the cheapest one on Ebay.
An accuracy of about 0.01 kPa should be possible.
The successor of the BMP085 is the BMP180, it's accuracy can be up to 0.002 kPa. It costs less than 10 dollars/euros on Ebay for a breakout board.

Patent: http://patent.ipexl.com/GB/GB2359374.html

I came across this sensor previously but I have my mirror chamber completely sealed so couldn't not mount it anywhere inside it. The only possible way is to find a sensor which has a mouth on which you can connect the tube from the pump which the MPXV5050V satisfies, considering the fact that the pressure inside the chamber = pressure on the tube

A typical automotive MAP sensor has a spigot for the pressure/vacuum connection and provides an analog output - it seems to be exactly what you need here, if the resolution of the Arduino 10-bit ADC is sufficient.

I wouldn't surprise me if inside a MAP sensor is a Freescale sensor of the MPX series.
After a little search I found that for example the MPXT4100 is used in a MAP sensor.
At first glance it seems indeed a better choice than the MPXV5050V, so I agree with PeterH.

I did check MPXT4100 but I feel comfortable in using the MPXV5050VC6T1CT-ND sensor. But I couldn't find the detailed pin connections for that. It has eight pins and based on the diagrams which I saw the connections involves only the first 4 pins.. please help

Datasheet: "Pins 1, 5, 6, 7, and 8 are no connects".
As far as I remember, it is even forbidden to connect them to anything, not even to ground.
I made this mistake with an MPX sensor. I soldered the unused pins to ground for better mechanical strength. But then I read that they may not be connected, so I had to redo my soldering.