Emerson Rosemount5081, Instruction Manual, Page: 46 / 152

4. Use the arrow keys to change to the desired temperature. To enter negative
numbers, press the left or the right arrow key until no digit is flashing. then press the
up or down arrow keys to display the negative sign.
The range is -5.0 to 130 °C.
5. Press ENTER to save. Press RESET to return to the main display.
NOTICE
If T AUTO was disabled in step 3, then the temperature entered in this step will be used in
all subsequent measurements, no matter the actual process temperature.
6.4 Set up custom curves (conductivity
measurements only)
Custom curves are used to correlate conductivity to concentration of the measured liquid.
The 5081 has programmable custom curves that can create a curve (second order) from
three to five user supplied points. If only two points are used, then a linear curve (straight
line) will be created. In order for the curve to be accurate, the data points acquired should
be taken from the liquid having the same reference temperature.
Best results are obtained by selecting data points that are representative of the typical
operating range and have at least 5% difference in conductivity values. It is recommended
that the graph of conductivity vs. concentration for the particular liquid is observed to
ensure that unsuitable points are avoided. Unsuitable points include conductivity values
with two concentrations associated with them. In addition to unsuitable points, record any
critical points - points that best describe the curve. Following these general guidelines will
provide optimal results.
The first point entered COND 1 should be at the normal operating condition. Other points
above and below COND 1 can then be entered. Nonlinear conductivity curves will require
additional data points to characterize these regions. Do not use the same data point more
than once and only use actual data (do not interpolate data points).
NOTICE
The default values for the custom curve are three data points: reference temperature of 25 °C
(77 °F) and a linear temperature slope of 2%/°C. This combination will yield the best results in
most applications. If the normal temperature is over 40 °C (104 °F) or under 10 °C (50 °F), the
reference temperature should be changed to the normal process temperature. If the
temperature slope at the reference temperature is known, then it can be used.
6.4.1 Setting up a custom curve
1. From the main menu, select PROG and then press NEXT four times.
SETUP CUST appears.
Programming - basics
36 Rosemount 5081