Procedimiento Calibración Presión y Temperatura Corus

CORUS PRESSURE & TEMPERATURE PROCEDURE OF CALIBRATION

 A.Laborde – February 2004

 A.

1° INTRODUCTION

The CORUS device integrates the capability to adjust/calibrate easily the temperature and the pressure on the field. This is performed through a linear function available both for pressure and temperature. Basically , the CORUS provides a temperature (T) and a pressure (P) for conversion factor calculation. The pressure P is calculated through 12 coefficients, linked to the sensor and initially programmed in the CORUS by Chasseneuil test bench. The P sensor can be represented by a Whestone bridge. CORUS measures at each conversion period the voltage of the bridge (Vp) and the impedance of the bridge (Zp). Then, CORUS computes the following formula to calculate P P = C1 + C2 Vp + C3 Zp + C4 Vp.Zp + …………..C12 Vp3.Zp2

On the top of this, it is possible to activate a linearisation function for field calibration into the CORUS. When activated the CORUS adjusts pressure and temperature as follow :  

T’ = (a x T) + b P’ = (c x P) + d

Then, only T ‘ and P’ are readable on the display and accessible through communication. When delivered from the factory :

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The linearization function is deactivated a= 1 ; c=1 ; b=0 ; d=0

2° FIELD CALIBRATION How to use linear function with WINCOR This function is protected by a restrictive access. When the user is inside the menu ‘Temperature’ or ‘Pressure’ , it is necessary to press “CTRL – L” sequence. Then, a password is necessary. The password is ‘ACT03’.

 After typing the code you are accessing to the following window:

You can click on “Modify” to change the coefficients for pressure and temperature.

 After selecting the one point or two points calibration mode, you must enter the theoretical value (measured with a reference material) together with the real value (displayed by the CORUS). When pressing on the button “Updating coefficients” the Wincor will calculate the new coefficients “a” and “b” to be programmed. You program these new values with the button “Prog”. The field “Activation” must be selected to activate the use of this function into the Corus. The reference material for pressure and temperature must be very accurate material (pressure generator and reference thermometer) with a valid periodical verification certificate, otherwise the test has no interest.

IMPORTANT : The access of this function is restricted into WINCOR (hidden menu + password) because it is a key function that modify the metrology of the device. Also, any modification of one of the concerned parameters (activation flag, coefficients a,b,c,d) required to put the programming switch ‘ON’ , meaning that such modification is possible only after the metrological seal has been removed if any.