H2O Rx DCH-2 User manual

CONDUCTIVITY-
TEMPERATURE
CONTROLLER
DCH-2
USERS GUIDE
DCH-2 Instruction manual PAGE 1

TABLE OF CONTENTS
SPECIFICATIONS......................... 3
SPECIFICATIONS (cont.).................. 4
INTRODUCTION. . . . . . . . . . . . . . . . . . . . . . . . . . 5
INSTALLATION .......................... 7
Instrument............................. 7
Electrode ............................. 7
4-20mA constant current output. . . . . . . . . . . . 8
Panelmounting......................... 9
OPERATION............................. 11
Initial check of the DCH-2. . . . . . . . . . . . . . . . . 11
TheLCDdisplay........................ 12
Selectingmodeofoperation............... 13
CALIBRATION OF THE DCH-2 . . . . . . . . . . . . . . 17
Calibratingconductivity................... 17
Pre-calibration of temperature . . . . . . . . . . . . . 17
Calibrating temperature with the electrode. . . . 18
Temperature compensation for conductivity. . . 19
Calibrating the compensation factor. . . . . . . . . 19
Settingcompensationfactor .............. 20
DCH-2 and high/low temperature alarm. . . . . . 21
OPTIONS................................ 22
WARRANTY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
PAGE 2 DCH-2 Instruction manual

SPECIFICATIONS
General features:
Display: 3 1/2 digit LCD display
Signal output: 4-20mA constant current output. Select
conductivity or temperature with DIP switch.
Output fully isolated from instrument.
Power: 240VAC 50Hz 7VA max.
Housing: Thermoplastic with transparent lid. Rated IP 55
Dimensions: 182(W) x 137(H) x 108(D)mm.
Conductivity
Range: 4 ranges selected with DIP switch under subpanel
0-199.0uS, 0-1999uS, 10-19,999uS,
10-199,999uS
Temperature
range: 0-100oC
Temperature
compensation: 0-100oC, fully automatic, compensation can be ad-
justed for no compensation to 20% compensation at
100oC Celsius.
Set point control: System 1 and System 2 can be configured
separately for up/down dosing with conductivity or
temperature.
Relay output: 2 relays with changeover contacts. Maximum rating
240VAC/Amps. (non inductive) Set point adjustment
fully independent over entire selected range.
Cell: 3/4" BSP thread inline type with moulded 4 pin socket
for cable connection.
(Immersion type available as
optional extra.)
Cell material: Polypropylene & stainless steel.
DCH-2 Instruction manual PAGE 3

SPECIFICATIONS (cont.)
Temperature
sensor: NTC thermistor type.
Sensor moulded into tip of electrode.
Temperature range of electrode 0-60oC.
Cable length: Three metres.
Temperature:
Range: 0oC to +199.9oC, (resolution 0.1oC)
Accuracy: +/- 1oC
Output control: 4-20mA constant current source
(internally selected)
4mA = 0oC, 12mA = 50oC, 20mA = 100oC
Sensor: NTC Thermistor type
(rated temperature range 0-250oC)
Size: 6mm Dia. x 120mm length.
Sensor body: 316 stainless steel with moulded 3 metres cable.
FIG.1 THE LCM-2 CONTROLLER
PAGE 4 DCH-2 Instruction manual

INTRODUCTION
The DCH-2 is well suited to operate in the hot and damp conditions
oftenpresentaroundboilers,coolingtowersandindustrialsitesingeneral.
Moisture and accidental sprays are sealed off from the sensitive parts of
the instrument with the transparent lid securely held in place with the 4
fasteners supplied with the unit. All cables feed through cable glands
situated on the underside of the DCH-2.
The LCD 3 1/2 digit display shows either temperature, conductivity or
SET POINT 1 and 2 when selected with the DISPLAY switch. Two small
red LED’s indicate the x1 or x1000 conductivity range selected. The
SYSTEM 1 and SYSTEM 2 controls with corresponding green LED’s
adjust the desired set point.
(See Fig.2)
The SET POINTS can be configured for up/down dosing, tracking the
conductivity or temperature. DIP switch 2 located under the subpanel set
the desired configuration.
3 1/2 LCD DIGITAL
DISPLAY
ADJUSTABLE SET
POINT 1 AND 2
WITH GREEN LED
LIGHTS ABOVE.
REMOVE SUBPANEL
FOR SCREW TERMI-
NALS, MODE
SELECTOR AND
CONDUCTIVITY FINE
ADJUSTMENT.
LED ARRAY TO INDICATE
UP/DOWN, SETPOINT
AND COND/TEMP MODE.
DISPLAY SELECTOR FOR
SET POINT
CONDUCTIVITY
TEMPERATURE.
FIG.2 FRONT PANEL LAYOUT
DCH-2 Instruction manual PAGE 5

A1AMPfusesituatedinsidetheenclosureonlyprotectstheinstrument.
The relays have change over contacts and require their separate fusing
to comply with safety rules.
Removing the sub panel reveals the screw terminals for all electrical
connections, configuration switches, calibrations for conductivity and the
temp.compensation.Thelegendfortheterminalsprintedonthesubpanel
allows an easy identification of the appropriate connections.
The DCH-2 can monitor and/or control conductivity and temperature
simultaneously in an installation with the proper selection of the SET
POINT configuration. The inherent accuracy of the 4-20mA constant
current output and electrical isolation makes it possible to interface into a
micro processor or logic controller to further expand the combination of
installations with the DCH-2.
(See 4-20 mA constant current output.)
FIG.3 TERMINAL CONNECTORS AND ADJUSTMENTS
PAGE 6 DCH-2 Instruction manual

INSTALLATION
Instrument
Installation and setting up of the DCH-2 is easy and straight forward.
No special tools are required.
(See Fig.2) The 4 screws are inserted
through 4 corner holes
(locking holes for the transparent lid) and also
fastened through them with a screw driver. All cables are fed through the
3 cable glandsand terminated at the appropriate terminals. Alwayscheck
that the stripped wire end is inserted above the small sliding metal block
inside the terminal to ensure proper connection when tightening the
terminal screw.
(See Fig.3)
If the control relays are used to switch 240VAC a wire link may be
connected between the 240V active terminal and the common contact of
the relays.
Electrode
The cell is mounted in line into a 3/4" BSP Tee. The T-piece used to
install the electrode must be PVC to ensure that no short circuit between
the stainless steel electrodes and pipe fitting occurs. A conduction leak-
age may also affect the accuracy of the instrument reading if a metal
T-piece is used.
The 4 core cable plugs into the 4 pin socket situated on the back of the
electrode. Never cut the cable or rejoin the 4 wires to shorten or lengthen
the cable, as this will result in unreliable and inferior performance. Always
reconnect the whole length of the cable to the 4 pin plug. Longer cables
up to 10 metres can be supplied on request.
The electrode in the standard package contains a 4 pin socket and a
3 metre cable. This greatly simplifies an installation where the cable is
wired through a conduit or is fastened to a walland the electrode screws
into a pipe. For situations where it is necessary to simply immerse the
electrode into the solution a special model with a 3 metre cable directly
moulded to the body can be supplied on request.
DCH-2 Instruction manual PAGE 7

The polypropylene electrode is used in applications with fluid tempera-
turesupto60
oC. A teflon electrode and the stainless steel temperature
sensorare usedforapplicationswithfluidtemperatureshigherthan60oC.
F The T-piece used to install the electrodeinline must be PVC to ensure
that the LCM-2 performs accurate and reliable.
4-20mA constant current output
Switch No. 5 of DIP switch 2 selects the conductivity or temper-ature
signal to drive the 4-20mA current output. The DISPLAY switch setting
has no effect on the selected mode of 4-20mA current output.
Conductivity range 0-200uS Conductivity range 0-2000
0uS = 4mA 0uS = 4mA
100uS = 12mA 1000uS = 12mA
200uS = 20mA 2000uS = 20mA
Conductivity range 0-20,000uS Conductivity range 0-200,000uS
0uS = 4mA 0uS = 4mA
10,000uS = 12mA 100,000uS = 12mA
20,000uS = 20mA 200,000uS = 20mA
Temperature range
0oC=4mA, 50
oC=12mA, 100 oC=20mA
F The DCH-2 now features a fully isolated 4-20mA output and can be
directly connected to other devices or micro processors withoutaffect-
ing the performance of the DCH-2.
The 4-20mA output is DC current. The signal wires therefore must be
connectedwiththerightpolarityobserved.Anyequipmentconnectedwith
reversed wires will not function at all!
PAGE 8 DCH-2 Instruction manual

F Normal coaxial cable such as TV cable may be used if desired with
the shield providing the negative connection.
Panel mounting.
Insert a round headed screw into the panel where the instrument is to
be attached. This screw determines the centre of the instrument location.
(See Fig.4) Slide the instrument over the slot opening at the back, check
that the unit hangs level and secure it with two screws inserted through
the slots at the two bottom corners.
FIG.4 ESCUTCHEON FOR THE DCH-2
DCH-2 Instruction manual PAGE 9

PAGE 10 DCH-2 Instruction manual

OPERATION
Initial check of the DCH-2
The LCD display, selected range light and a combination (depend-ent
on the instrument configuration) of the small LED’s will light up once the
instrument is properly installed and the power connected. The two output
relays may latch depending on the position of the SET POINT controls.
Select TEMP. with the DISPLAY switch and ensure that the reading
shows the approximate temperature of the liquid. With the DIP switch 1
select the desired uS range. Observe that
the x1 or x1000 red LED lights up and the
decimal point of the LCD display shows in
theplaceaccordingtotherangeselected.
(See “The LCD display") Select SET 1 and
SET 2 and rotate the corresponding SYS-
TEM 1 and SYSTEM 2 controls to test the
display for a proper readout of the set uS
value. The minimum reading is 000 and will
go into over range
(blank display) just be-
fore reaching maximum range with the set
point control. Now select uS with the DISPLAY switch. The approximate
uS value will be displayed.
F When sweeping across the range with the SET POINT control the
operation of the relay appears to function in the reverse order. This
however is only an illusion as it is obvious that the SET POINT is
changing and not the value of the solution.
FIG.5 LED arrangement for the
DCH-2
DCH-2 Instruction manual PAGE 11

The LCD display
The digital readout displays temperature, conductivity and the SET
POINT1and2whenselectedwiththeDISPLAYselector.
4 conductivity ranges can be selected with the LCM-2 instrument.
0-199.9uS The LCD display shows the measured value in uS
directly with a resolution of 0.1uS.
(TABLE 1)
1-1999uS
The LCD display shows the measured value in uS
directly with a resolution of 1uS.
(TABLE 2)
10-19,999uS
The displayed reading is multiplied by 1000 to get the
correct measured value. Resolution of this range is
10uS
(TABLE 3)
100-199,999uS
The displayed reading is multiplied by 1000 to get the
correct measured value. Resolution of this range is
100uS.
(TABLE 4)
FIG.6 THE DIFFERENT RANGE SETTINGS OF THE DCH-2
PAGE 12 DCH-2 Instruction manual

Selecting mode of operation
The mode of operation is performed with the DIP switch 2. System1
and System2 work independent of each other and can be configured for
conductivity or temperature control. SW1 and SW2 select the up/down
mode of the relay versus the set point operation. SW3 and SW4 select
the desired mode of control. SW5 selects temperature or conductivity
tracking of the 4-20mA current out-put. The combinations of operation
with these settings are to numerous for all to be mentioned here. Fig.7
gives some examples for various configurations.
FIG.7 CONFIGURATION OF THE CONTROLS
DCH-2 Instruction manual PAGE 13

FIG.8 USED IN CHEMICAL ADDITION
FIG.9 AUTOMATIC BOILER TDS BLOWDOWN
PAGE 14 DCH-2 Instruction manual

FIG.10 AUTOMATIC COOLING TOWER BLEED
FIG.11 USED WITH A RINSE TANK
DCH-2 Instruction manual PAGE 15

FIG.12 CRH-41 RECORDING TEMPERATURE
PAGE 16 DCH-2 Instruction manual

CALIBRATION OF THE DCH-2
Calibrating conductivity
For best performance use buffers nearest the uS range actually used
in the installation. To adjust the calibration place the electrode in a known
buffer solution.
F Always check the temperature measurement before any conductivity
adjustments are done as the electrode is temperature dependent.
Calibrating the ranges 0-200 / 1-2000 / 10-20,000 uS
SelectuS mode with the DISPLAY switch. Selecttheappropriaterange
for the correct buffer range. Remove the sub panel. With a small screw
driver adjust potentiometer P1 for the correct uS setting.
Calibrating the range 100-200,000 uS
Potentiometer P1 and P2 adjust this range. P2 however only affects
this range and is used if the calibration cannot be achieved with P1alone.
Pre-calibration of temperature
Follow the same set-up procedure as described for the coarse adjust-
ment. Disconnect the two wires of the temperature sensor and replace
with a resistance of 1.35 KOhms. (Use a 5K and a1.8K resistor in parallel
or use a 5K potentiometer and adjust to the 1.35K value using a digital
multimeter.) Remove the metal cover situated under the subpanel. Set
DISPLAY to TEMP, then turn potentiometer No.1 (temp. OFFSET) to the
highestreadingpossible.
(fullyclockwise) WithpotentiometerNo.2 (temp.
SPAN)adjustthedisplayedtemperature to read 72.0oC. Use potentiome-
terNo.1toreducethereadingbackto25.0oC.Reconnectthetemperature
sensor that willnow track the temperature withan accuracy of aprox. 2oC.
This calibration will be adequate for most applications that use the
temperature only for compensation purposes.
DCH-2 Instruction manual PAGE 17

Calibrating temperature with the electrode
Select TEMP. mode with the DISPLAY switch. Place the sensor into a
sample of water with a max. temperature of not more than 4-5oC. Wait for
10 min. for the sensor to stabilize. Adjust potentiome-ter No.1 (temp.
OFFSET)untilthedisplaycorrespondswiththeactualtemperature.Place
the electrode into water with a temperature of at least 50oC, wait 15 min.
and use potentiometer No.2 (temp. SPAN) to adjust the reading.
(See
Fig.13)
F The standard polypropylene electrode takes aprox. 15 min to track
temperature changes of 50oC. If the installation requires an accurate
and fast tracking of temperature or conductivity the stainless steel
temperaturesensor TS-316mustbeused inplaceofthebuild-intemp.
sensor.
POTENTIOMETER No.1
TEMP. OFFSET
POTENTIOMETER No.2
TEMP. SPAN
FIG.13 ADJUSTMENTS FOR TEMPERATURE
PAGE 18 DCH-2 Instruction manual

CalibTTemperature compensation for conductivity
The electrical signal from a conductivity electrode increases with a rise
in temperature of the fluid being controlled. A conductivity controller has
to compensate for this by reducing the sensitivity of the instrument to
maintain an overall accuracy of measurement. The DCH-2 has a com-
pensation factor set at 0.2 that means the conductivity gain reduces by a
factor of 5 with a temperature increase of 100oC. This performance will
suit most applications, however the compensation factor can easily be
adjusted for individual installations.
(See below)
Calibrating the compensation factor
Select the 1-2000uS range. Remove the electrode wires from the
terminal. Connect a 1KOhm resistor across the conductivity input and a
5KOhmpotentiometeracrossthe temperatureinput.SwitchtoTEMPwith
the DISPLAY selector. Adjust the connected potentiome-ter until the
display reading shows 100oC. Select uS with the DISPLAY switch. Turn
the potentiometer P3 situated with the calibration potentiometers
(temp.compensation) fully anti-clock-wise until the maximum uS reading
is achieved.
(Compensation is set to 0) With the calibration potentiometer
P1 (conductivity adjust.) select 1000uS. Calculate 20% of the dialed
number (200uS)and with potentiometer P3 align the displayed uSto read
the calculated value. The LCM-2 is now compensated to the standard
scale. This procedure is also used to calibratefor other different compen-
sation factors if there calculated value is known. ie.(0.4 = 40% = 400uS)
F Allcalibrationproceduresdescribed herecan begreatly simplifiedwith
a
HOFMANN uS/temperature simulator CMH-2
DCH-2 Instruction manual PAGE 19

Setting the compensation factor with batch samples
Thefast respondingstainlesssteel sensor TS- 316 is preferable for
this operation. Use a batch sample with as low a temperature as
possible.
(max 20oC) First check temperature for proper reading and
recalibrate if necessary.
(See temperature)
Check and calibrate the displayed uS (See uS calibration) to the
known value. Seal the container with the batch sample to avoid
evaporation that would give an erroneous reading throughconcentra-
tion of the PPM. Heat the liquid to above 50oC. Check and adjust
(if
necessary)
the temperature. Select uS and read the displayed value.
Any deviation of uS from the first measured value is corrected with
the potentiometer P3.
(Compensation factor)
This procedure should now be repeated a few times to obtain a
reasonable accuracy. The compensation adjustment made at the
higher temperature will also have an effect at the lower temperature
setting ifthe first temperature set up issubstantially higher than10oC.
It is apparent that both adjustments are interactive with each other
and a slight allowance should be made when correcting the uS value
or the compensation factor to avoid numerous repetitions of this
procedure.
F The temperature reading displays an over-range mode (showing
a 1 and three blank digits) if the sensor is faulty or a connection to
the DCH-2 becomes open circuit.
PAGE 20 DCH-2 Instruction manual