Yokogawa Button Operated DX2000 Manual de usuario descargar pdf (Pagina 12)

Computing example of the display value accuracy

¾ Integration time 50 Hz

¾ 2 V range Voltage span 0.0000 to 1.0000 V

¾ LOG span -2 to 3

1) Determine the converting equation for the setting.

• Y = 10

(SU-SL)*(X-VL)/(VU-VL)+SL

= 10

(3-(-2))*(X-0)/(1-0)+(-2)

= 10

(5X-2)

2) Determine the measurement error with respect to the input voltage.

• Measurement accuracy of the 2 V range = ±(0.05% of rdg + 12 digits)

= ±(0.0005*10000+12)

= ±17 digits

• Therefore, for an input voltage of 1 V, the value will fall within the range

between 0.9983 V and 1.0017 V.

• Since the computation is performed on the negative side with large error in

the LOG characteristics, we obtain X

err

= 0.9983 V.

3) Determine the hardware error of the display value.

• Substitute X

err

, the value determined in 2), into the equation of 1).

err

= 10

(5*0.9983-2)

= 9.8 * 10

(truncate values below the one-hundredths place)

• Since the true value is Y = 1.0 * 10

, the error is 2 digits.

• Therefore, the hardware error of the display value is given by Y’ = ±2 digits.

4) Display value accuracy of the mantissa

• As a final error, we add the software error to the hardware error.

• Software error = Hardware error * 1.1 + 1 digit

• Display value accuracy = ±(2 digits * 1.1 + 1 digit)

= ±(3.2 digits)

• The fraction is rounded up. When the mantissa is 2 digits, the display

accuracy is ±4 digits.

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Yokogawa Button Operated DX2000 Manual de usuario Pagina 12