Pressure sensor/-gauge calibration device

You can also use your own calibration device in your process different ways. Here are some examples outside basic calibration area:

You can use pressure calibration device anywhere you need pressure with small volume. The device is designed to be used from 0 to 1000 bar absolute pressure and it will generate vacuum when needed.

Pressure calibration system consists of

Pressure adjustment is based on device that generates pressure and controls it without even smallest inconsistancy when rising/falling and when stopping the adjustment. This pressure rise and fall will happen without any steps, in completely smooth curve. Pressure is as adjustable on 0-1 bar scale as on 0-800 bar scale.

Pressure rise is based on degreasing pressurised volume in steples way. With piston- and pump operated aplications there is always inconsistancy in pressure development due to seal deformation, friction changes and piston direction changes. Big Muddy came up with a solution in which the line between stationary friction and dynamic friction is not an issue anymore. The friction is controlled continuously which results rising and falling pressure without any steps or direction changes while making measurements.

This method is not based on 4 to 5 points on scale which are written on paper with not actually knowing in which directon the pressure is developing if you look at it close enough. This method is the only method that you can use if you want to know the accuracy of the pressure transmitter/sensor full scale with actual hysteresis.

Reference sensor

When you need to use pressure for calibration, you need to know the pressure. Reference sensor is used to measure the pressure at the same time and at the same pressurised space (Fluid pressure is same everywhere in one space when there's no flow). This reference value will be used as traceable result when you are calibrating or adjusting your sensor/transmitter.

Reference sensor must be traced to international measurement norms. This means that your process sensor will be traced to the reference sensor, on which the error is known 3 to 5 times more accurately than your process sensor's error. This reference sensor error is traced to the one used calibrating that one and so on.. until all stops to Paris (International measurement norms are held in Paris). You can buy your reference sensor with a calibration certificate but if this is not an option, you can calibrate the reference sensor in acredited calibration laboratory.

Reference sensor accuracy defines the accuracy you will get in calibrating your own sensors. The most common rule is Calibration norm should be at least three times the accuracy of the calibrated item.

Software

Now you have developed the pressure and you can control it accurately. You also know the pressure and you could see the difference if you had eye quick enough.. Now its time to let computer do the work!

Big muddy has developed a computer software based on Labview-environment. This software monitors both the reference sensor and sensor(s) that you calibrate. The difference is measured and stored to be used in calibration calculations and a report. Values are also used in zero point check (zero point can often be moved by adjusting the sensor). Software recommends corrective actions if necessary. After corrective actions you can calibrate the sensor again with new values to get a report up to date.

In picture below is an example of customer's (Sampo-Hydraulics Oy) calibration report made by Big Muddy software. (Click to enlarge):

The software is designed for maximum of three calibrations at the same time. One pressure rise from zero point to maximum and back to zero will be enough data for calibrating three sensors with the same pressure range. All three sensors have their own calibration certificates after this procedure.

Calibration certificates are saved to a specific directory and the software updates it's database every time a new sensor will be calibrated. When you will calibrate the same sensor next time, the software suggests you the values and ranges based on sensor's serial number. Please check this video, in which three Hydrotechnik 0-600 bar sensors are calibrated at once.

Other stuff

Here is a chart in which you will see all different parts of the calibration system and how they are linked to each other. (Please click on the picture to enlarge it):