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PRESYS
Instruments
To verify the step values of a program, select the VARIABLE option and confirm
the values shown in the display with the key ENTER. The 10%, 20% and 25% options
change the number of steps automatically and recalculate the values according to
SETPOINT HIGH and SETPOINT LOW.
PRBe: This option enables the use of an external probe for the dry block
temperature control when selecting YES. In order to use the internal probe, select NO.
When enabling the external probe, configure the probe calibration parameters in the
PARAM menu and the temperature unit in CF as degrees Celsius or Fahrenheit. The
calibration parameters correspond to the R
Callendar-Van Dusen equation:
R(t) = R
This equation is generally used in the IPTS-68 temperature scale, where t
refers to the temperature in this scale and R
can also be used in the ITS-90 scale.
The menu for the configuration of these coefficients is shown below:
To enter the value of a coefficient, it must be split into a mantissa and an
exponent as it is used in scientific notation. For a C coefficient equal to -3.151052×10
for example, type its mantissa (an integer and a fractional part with six digits) in the C
mnemonic and its exponent, as an absolute value, in the E_C mnemonic. In this way,
C = -3.151052 and E_C = 2.
Note that the signal can be inverted by pressing the key ZERO when the number
on the display is zero. This changes the signal from + to -, or vice-versa.
The coefficients for the ITS-90 scale according to the IEC-60751 standard are shown
below:
MD: Maximum deviation from the set point for the temperature control with an
external probe. The temperature is stabilized by the control after it enters in the range
limited by SET ± MD. This parameter must be configured as 1.0 °C.
SC: This function scales the input reading. The scaling is very useful in
temperature transmitter calibration, for instance, because it displays the current
temperature and the transmitter reading (mA) in the same unit. Thus, the error can be
verified directly in °C or °F. Select the option SC and press ENTER. If no input is
selected in IN, the calibrator will show the SELECT INPUT FIRST message. In this
case, go to menu IN and select the input signal type.
{1 + A.t + B.t
0
R0
A
E_A
E_B
R
= 100.00000
0
A = +3.908300
B = -5.775000
C = -4.183000
, A, B, and C coefficients of the
0
.(t – 100 °C)}, C = 0 for t ≥ 0.
2
3
+C.t
to the resistance at 0 °C. However, it
0
B
C
E_C
E_A = -03
E_B = -07
E_C = -12
T-650PH
-2
,
Page 11
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