Key Functions; Programming The Parameters - Delta OHM DO 9785T Bedienungsanleitung

DO 9785T/DO 9765T pH transmitters convert the output of a pH electro-
de, with temperature compensation, into a signal at 4÷20 mA.
The pH electrode input circuit is galvanically insulated against the 4÷20 mA output
signal.
An LCD indicator allows viewing of the process signal value and of the various para-
meters.
The accurate design and choice of components make the instrument precise and
reliable for a long working life.
The instrument works in conjunction with a pH electrode or Redox and a temperatu-
re probe (Pt 100 sensor, 100 Ω at 0°C).
Characteristics
Technical characteristics
pH -1.00 pH...15.00 pH (-500...+500 mV)
ORP -1999...+1999 mV
Input impedance >10 Tohm
Cable length <50 metres screened (about 5 nF)
Accuracy 0.1% of reading ±1 digit ±0.01% pH per °C of drift
in temperature
Pt100 2/4 wires -50...199.9°C
Transducer energizing 0.5 mA DC
Cable length <10 metres unscreened
<50 metres screened (about 2 nF)
Accuracy 0.2°C ±0.1% of reading ±2 digits ±0.01°C/°C
Automatic According to Nernst
Manual -50°C÷200°C
4.00...20.00 mA Programmable and proportional to the pH or mV value
Accuracy 0.5% of reading ±0.02 mA
Insulation 2500 Vac 1 minute
A and B Bistable, contact 3A/230 Vac free potential
Passive 4÷20 mA, 2 wire configuration, 10÷35 V, see fig. 2
Active 24 or 230 Vac - 15/+10% 1 VA, 48...62 Hz, see fig. 1
External dimensions 120x122x56 mm
Protection class IP64
External dimensions 94x96x126 mm
Protection class IP54
Safety EN61000-4-2, EN610120-1 level 3
Electrostatic discharge EN61000-4-2 level 3
Fast electric transients EN61000-4-4 level 3
EN61000-4-5 level 3
Voltage variation EN61000-4-11 level 3
Susceptibility to IEC1000-4-3
electromagnetic interference
Emission of electromagnetic EN55020 class B
interference

Key functions

PRG Programming of the parameters is activated by pressing the PRG key plus
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the and keys. The message P1 appears on the display, indicating that
the parameter P1 is being programmed. When the PRG key is pressed
continuously, the messages P2, P3, P4, P5, P6, P7 and the corresponding
parameters are displayed in sequence. After P7 the instrument returns to
normal function.
SET Key for setting the relay intervention threshold. The ON or OFF symbol
appears on the display, indicating the switching on or off threshold of relay
A or of relay B.
°C/°F - If this key is pressed it changes the temperature measuring unit to
degrees Celsius or degrees Fahrenheit.
- When pressed together with the CAL key it activates the manual tempe-
rature setting function.
- If pressed during the conductivity calibration function it quits the calibra-
tion function without storing the calibration.
pH/mV - If this key is pressed it changes the measuring unit to mV or pH.
- When pressed together with the CAL key it activates the pH calibration
function.
OK Confirms the programming parameters, or the relay SET values, and sto-
res them.
CAL - When pressed together with the °C/°F key it activates the manual tempe-
rature setting function.
- When pressed together with the pH/mV key it activates the pH calibration
function.
- Key used to confirm pH calibration and manual temperature calibration.
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- Key for increasing the value displayed in the parameter programming
phase.
- During the relay SET point programming phase.
- During the calibration phase.
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- Key for decreasing the value displayed in the parameter programming
phase.
- During the relay SET point programming phase.
- During the calibration phase.
Setting the relay SET point
- Press the SET button; the ON symbol appears on the display with the letter A to
indicate that the value shown corresponds to the switching on threshold of relay A.
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- To change this value press the
- Press SET; the OFF symbol appears with the letter A to indicate that the switching
off threshold of relay A is being displayed.
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- To change this value press the
- Press the SET button; the ON symbol appears on the display with the letter B to
indicate that the value shown corresponds to the switching on threshold of relay B.
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- To change this value press the
- Press SET; the OFF symbol appears with the letter B to indicate that the switching
off threshold of relay B is being displayed.
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- To change this value press the
- Press SET, the instrument stores the values and returns to normal function.
NOTE: During the SET point setting phase (symbols ON or OFF lit) the instrument
returns to normal function if no key is pressed for 2 minutes.
Temperature setting for manual compensation
If the temperature probe is not connected or if the probe is broken the measuring
unit °C or °F flashes. In this case it is possible to set the temperature compensation
value manually.
- Press the CAL key and the °C/°F key together; the message CAL appears at the
bottom of the display.
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- Using the and keys, set the temperature value corresponding to the tempera-
ture of the liquid in which you wish to measure the pH value.
- Press CAL to confirm this value. The message CAL disappears.
Calibration of the DO 9785T/DO 9765T with pH electrode
Calibration of the offset of the pH electrode:
- Immerse the electrode in the buffer solution used for calibrating the offset (6.86 pH).
- Press the CAL key and the pH/mV key together; the message CAL appears at the
top of the display.
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- Using the and keys, adjust the pH value measured as a function of the liquid
temperature.
- Press CAL to confirm this value. The message CAL disappears.
Calibration of the slope of the pH electrode:
- Immerse the electrode in the buffer solution used for calibrating the slope (4.01 or
9.18 pH).
- Press the CAL key and the pH/mV key together; the message CAL appears at the
top of the display.
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- Using the and keys, adjust the pH value measured as a function of the liquid
temperature.
- Press CAL to confirm this value. The message CAL disappears.
NOTE: If you want to quit without storing the new calibration, press the °C/°F key.
N.B.: The instrument can automatically recognize three standard calibration solu-
tions: 4.01 pH, 6.86 pH and 9.18 pH.

Programming the parameters

P1 Relay control unit and analog output, pH or mV.
P2 pH/mV value corresponding to 4 mA at output. May be set between -1.00 pH
and 15.00 pH or between -1999 mV and +1999 mV.
P3 pH/mV value corresponding to 20 mA at output.. May be set between -1.00 pH
and 15.00 pH or between -1999 mV and +1999 mV.
P4 Delay time in the intervention of relay A. May be set between 0 and
255 seconds.
P5 Delay time in the intervention of relay B. May be set between 0 and
255 seconds.
P6 Calibration of Pt100 probe, calibration of output in current, calibration of out-
put in voltage.
(Calibration procedure to be carried out at a laboratory by skilled
workers).
P7 Display of the offset voltage value and of the slope value of the electrode.
To change one of these parameters press key PRG until the message correspon-
ding to the parameter to be changed appears on the screen. Using the
keys, bring the parameter displayed to the desired value. Press OK to confirm.
Parameter P7 cannot be altered.
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