Etatron AG-SELECT-BCD Serie Manual Del Usaurio página 10

Calibrating the analog output
- Press the PRG key until the message P8 appears on the display.
- Connect a precision milliammeter to the analog output.
- Press the CAL key twice; the message CAL appears at the top of the display
and the message 4.0 at the bottom, indicating calibration at 4 mA.
s t
- Using the and keys, adjust the value of the output current so as to have an
indication of 4,000 mA on the precision milliammeter.
- Press the CAL key; the message CAL appears at the top of the display and the
message 20.0 at the bottom, indicating calibration at 20 mA.
s t
- Using the and keys, adjust the value of the output current so as to have an
indication of 20,000 mA on the precision milliammeter.
- Press OK to confirm.
Display
Symbol Description
°C indicates that the value shown is in °C.
°F indicates that the value shown is in °F.
µS indicates that the unit of the value shown is micro Siemens.
mS indicates that the unit of the value shown is milli Siemens.
A indicates that the relay A is in closed status.
B indicates that the relay B is in closed status.
ON indicates that the value shown corresponds to the closing thresholds
of the contacts of relay A or B.
OFF indicates that the value shown corresponds to the opening thresholds
of the contacts of relay A or B.
Error signals
OFL - Warning which appears during measurement when the value to be
displayed is out of scale.
E1 - Error warning which appears during conductivity calibration to indicate that
the probe gain is too high. Press P2 to increase the cell constant value.
E2 - Error warning which appears during conductivity calibration to indicate that
the probe gain is too low. Press P2 to decrease the cell constant value.
E3 - Error warning which appears to indicate that the instrument is unable to
recognize the buffer solution used for automatic calibration. Press the or
key to make this indication disappear.
E4 - Reading error on the EEPROM.
Order code
AG-SELECT RCD: Conductivity transmitter 4÷20 mA passive or active, power
supply 24 Vac with double display 96x96 mm, for panel
mounting.
AG-SELECT BCD: Conductivity transmitter 4÷20 mA passive or active, power
supply 24 Vac with double display 122x120 mm, for use on
the field.
SPT 86: Combined industrial conductivity and temperature probe in
POCAN with 4 platinum electrodes, cell constant K = 0.7, 1.5
meters cable, Pt100 with 2 wires. Temperature 0÷90°C.
SPTKI 10: Combined industrial conductivity probe in Glass with 2 black
oxidized platinum electrodes, cell constant K = 1, S7/PG13
screw-joint, 2 wires output: eurostandard S7. Temperature
0÷100°C.
SPTKI 11: Combined industrial conductivity and temperature probe in
Ryton with 2 graphite electrodes, cell constant K = 1, 5
meters cable, Pt100 with four wires. Temperature 0÷50°C.
HD 882 M100/300: Temperature probe with Pt100 sensor, miniature head, shaft
∅ 6x300 mm.
HD 882 M100/600: Temperature probe with Pt100 sensor, miniature head, shaft
∅ 6x600 mm.
HD 8712: Calibration solution 0.1 mol/l corresponding to 12,880 µS/cm
at 25°C.
HD 8714: Calibration solution 0.01 mol/l corresponding to 1413 µS/cm
at 25°C.
APPENDIX
Table of compatibility between range and sensor
Conductivity range
0.01÷0.2
√
0÷19.99 µS
√
0÷199.9 µS
√
0÷ 1999 µS
√
0÷199.9 mS
0÷19.99 mS
0÷199.9 mS
0÷ 1999 mS
Nominal cell constant
0.2÷2 2÷20 20÷199.9
√
√ √
√ √ √
√ √ √
√ √
√
Temperature sensor
Temperature Pt100
80.25 Ω
-50°C
90.15 Ω
-25°C
100.00 Ω
0°C
109.73 Ω
25°C
119.40 Ω
50°C
128.98 Ω
75°C
Calculating the temperature coefficient of a solution
If the temperature coefficient of the solution is not known, it may be determined
using the AGSELECT-RCD/BCD
- Set the temperature coefficient at 0.0%/°C (parameter P1).
The following measurements should be taken as close as possible to the work
point, between 5°C and 70°C, for greater accuracy.
- Immerse the probe in the testing liquid. Wait for the measurement to become
stable.
- Take note of the temperature and of the conductivity.
- Increase the solution temperature by at least 10°C.
- Take note of the temperature and of the conductivity.
- Calculate the temperature coefficient using the following formula:
(Gx-Gy) x 100%
α =
Gy(Tx-20) - Gx(Ty-20)
Where:
Gx conductivity at temperature Tx
Gy conductivity at temperature Ty
N.B.: if the reference temperature is 25°C, replace 20 with 25.
- Set the temperature coefficient with the value calculated as above (parameter
P1).
Calibration of the instrument for measuring conductivity
The conductivity measurement depends strongly on the temperature of the liquid
that is to be measured; this relationship must be considered during calibration.
Calibration of the instrument alone by means of a precision
resistance
This is a sure and accurate method for calibrating the instrument alone, but it
does not allow for the variations of the cell constant that may occur, nor of the
state of efficiency and cleanness of the cell.
The precision resistance used for calibration will be chosen according to the scale
that you want to calibrate. Typical values are the following:
Conductivity
100,0 µS
500,0 µS
1000 µS
5000 µS
10,00 mS
50,00 mS
100,0 mS
500,0 mS
1000 mS
The precision resistance will be connected to the end of the cable that connects
the probe to the instrument. This ensures greater accuracy of calibration.
Disable the temperature compensation α
with the precision resistences.
Calibration with standard solutions
In this case too, for the calibration of the instrument, cable and measuring probes
in a standard solution, the greatest attention must be paid to the temperature of
the solutions and the cleanness of the measuring cell. It is advised not to carry out
calibration below 500 µS/cm. Solutions with low conductivity must be kept closed
in their containers. Contact with the air increases their value due to the absorption
of CO .
2
The regulations for the preparation of standard solutions with a base of KCl dis-
solved in water with a high degree of purity supply the method and percentages of
KCl and water to be mixed.
ETATRON D.S. supplies two solutions for calibration:
HD 8712 Calibration solution at 12,880 µS/cm at 25°C
HD 8714 Calibration solution at 1430 µS/cm at 25°C
Care and maintenance of the conductivity cell
In conductivity measurement systems in industrial plants, if the installation is cor-
rectly made, readings are generally reliable for a long time. The important thing is
to carry out correct, programmed maintenance of the measuring cell.
Abrasion of the cable due to continued swinging movements must be avoided, as
6
Temperature Pt100
138.50 Ω
100°C
147.94 Ω
125°C
157.32 Ω
150°C
166.62 Ω
175°C
175.47 Ω
199°C
(reference temperature 20°C)
Resistance
10000 Ω
2000 Ω
1000 Ω
200 Ω
100 Ω
20 Ω
10 Ω
2 Ω
1 Ω
during the calibration of the instrument
Τ