Hanna Instruments PH 500 User Manual

5 (2)

pH 500/mV 600 Series

Panel-mounted,

Microprocessor-based

Process pH/mV Meters

Instruction Manual

Dear Customer,

Thank you for choosing a Hanna Product.

This instruction manual has been written for the following products:

pH 500111 pH Controller with single setpoint, ON/OFF control, analog output

pH 500112 pH Controller with single setpoint, ON/OFF control, RS232 output

pH 500121 pH Controller with single setpoint, proportional and ON/OFF control, analog output

pH 500122 pH Controller with single setpoint, proportional and ON/OFF control, RS232 output

pH 500211 pH Controller with dual setpoint, ON/OFF control, analog output

pH 500212 pH Controller with dual setpoint, ON/OFF control, RS232 output

pH 500221 pH Controller with dual setpoint, proportional and ON/OFF control, analog output

pH 500222 pH Controller with dual setpoint, proportional and ON/OFF control, RS232 output

mV 600111 ORP Controller with single setpoint, ON/OFF control, analog output

mV 600112 ORP Controller with single setpoint, ON/OFF control, RS232 output

mV 600121 ORP Controller with single setpoint, proportional and ON/OFF control, analog output

mV 600122 ORP Controller with single setpoint, proportional and ON/OFF control, RS232 output

Please read this instruction manual carefully before using the instrument. It will provide you with the necessary information for the correct use of the instrument, as well as a precise idea of its versatility.

These instruments are in compliance with directives.

All rights are reserved. Reproduction in whole or in part is prohibited without the written consent of the copyright owner, Hanna Instruments Inc., 584 Park East Drive, Woonsocket, Rhode Island, 02895 , USA.

2

TABLE OF CONTENTS

PRELIMINARY EXAMINATION . . . . . . . . . . . . . . . . . 4 GENERAL DESCRIPTION. . . . . . . . . . . . . . . . . . . . . 4 FUNCTIONAL DESCRIPTION . . . . . . . . . . . . . . . . . 6 MECHANICAL DIMENSIONS . . . . . . . . . . . . . . . . . 7 SPECIFICATIONS pH 500 & mV 600 . . . . . . . . . . . . 8 INSTALLATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 SETUP MODE . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 CONTROL MODE . . . . . . . . . . . . . . . . . . . . . . . . 17 IDLE MODE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 ANALOG OUTPUT . . . . . . . . . . . . . . . . . . . . . . . . 23 RS 232 COMMUNICATION AND DATA LOGGING 25 CALIBRATION . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 LAST CALIBRATION DATA . . . . . . . . . . . . . . . . . . . 39 STARTUP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 FAULT CONDITIONS AND SELFTEST PROCEDURES . 43 pH VALUES AT VARIOUS TEMPERATURES . . . . . . . . 47 ELECTRODE CONDITIONING AND MAINTENANCE . 48 TAKING REDOX MEASUREMENTS . . . . . . . . . . . . . 52 ACCESSORIES . . . . . . . . . . . . . . . . . . . . . . . . . . . 54 WARRANTY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60 CE DECLARATION OF CONFORMITY . . . . . . . . . . . 62

3

PRELIMINARY EXAMINATION

Remove the instrument from the packing material and examine it carefully to make sure that no damage has occurred during shipping. If there is any noticeable damage, notify your Dealer or the nearest Hanna Customer Service Center immediately.

Note Save all packing materials until you are sure that the instrument functions correctly. Any damaged or defective items must be returned in their original packing materials together with the supplied accessories.

GENERAL DESCRIPTION

The product is a real time microprocessor-based pH/ORP controller. It provides accurate measurements, flexible ON/OFF or proportional control capabilities and dual alarm signals.

The system is composed of a case inside which the signal conversion circuitry, the microprocessor circuitry and the output power drivers are contained.

MAIN FEATURES OF DIFFERENT MODELS

Display: large LCD with 4 ½ 17 mm digits and 3 ½ 10 mm digits.

LEDs: three (mV 600) or four (pH 500) LEDs are provided for signaling the energizing of relay 1 (a yellow led), relay 2 (a yellow led in pH 500 Series only) and alarm relays (a green and a red LED).

Relays: 1 or 2 output relays for acid or base dosage (COM, NO and NC contacts) and 1 output relay for alarm condition (COM, NO and NC contacts).

RS232 isolated communication link (optional).

Calibration and Setup procedures allowed only through an unlock password.

Calibration: for pH 500 Series in 1, 2 or 3 points with buffers 4.01, 7.01 and 10.01 pH (25 °C); for mV 600 Series in 1 or 2 points at 0, 350 and 1900 mV.

Temperature compensation of the HANNA standard buffers (for pH 500 Series only).

4

Temperature compensation of the pH reading (for pH 500 Series only).

Manual temperature setting when the temperature probe is not inserted or temperature exceeds the upper range.

Last calibration data internally recorded (non-volatile EEPROM memory): calibration date and time, pH offset, pH slopes, number of calibration points and correspondent pH values (for pH 500 Series only) or calibration date and time and the mV calibration points used (for mV 600 Series only).

Input: pH electrode with BNC connector.

Output:

-isolated 0-1 mA, 10 KΩ maximum load (optional);

-isolated 0-20 mA, 750 Ω maximum load (optional);

-isolated 4-20 mA, 750 Ω maximum load (optional);

-isolated 0-5 VDC, 1 KΩ minimum load (optional);

-isolated 1-5 VDC, 1 KΩ minimum load (optional);

-isolated 0-10 VDC, 1 KΩ minimum load (optional).

Real time clock.

5

FUNCTIONAL DESCRIPTION

FRONT PANEL

 

 

 

 

 

 

 

1.

Liquid Crystal Display

2.

LCD key

exits from setup and calibration modes and reverts back to

 

 

normal mode (in idle or control phases with the measure-

 

 

ment on the display). In pH 500 series, during pH

 

 

calibration, alternately displays pH buffer value or current

 

 

temperature

3.

SETUP key

enters setup mode

4.

CAL DATA key

last calibration data viewing (enters and exits)

5.

CAL key

initiates and exits calibration mode

6.

key

increases the blinking digit/letter by one when selecting a

 

 

parameter. Advances forward while in last calibration data

 

 

viewing mode. Increases the temperature setting when

 

 

temperature probe is not inserted

7.

key

decreases the blinking digit/letter by one when selecting a

 

 

parameter. Reverts backward while in last calibration data

 

 

viewing mode. Decreases the temperature setting when

 

 

temperature probe is not inserted

8.

key

moves to the next digit/letter (circular buffer) when select-

 

 

ing a parameter. Same as key during last calibration

 

 

data viewing mode

9.

CFM key

confirms current choice (and skips to the next item)

10.

LEDs

 

 

 

 

 

6

REAR PANEL

1.RS232 Connection Port (pH500XY2 and mV600XY2 models only)

2.Analog Output (pH500XY1 and mV600XY1 models only)

3.Power Supply Input

4.Alarm Terminal

5.Relay 2 - Second Dosing Terminal (pH5002XY models only)

6.Relay 1 - First Dosing Terminal

7.Connections for Pt 100 Temperature Sensor

8.Connection for Electrode Reference

9.Connection for Potential Matching Pin

10.BNC Socket for pH or ORP Electrode

11.±5V Power Supply Output

Unplug the meter before starting any electrical connections.

MECHANICAL DIMENSIONS

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

FRONT VIEW

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

SIDE VIEW

 

 

7

SPECIFICATIONS pH 500 & mV 600

Range

0.00 to 14.00 pH

(pH 500 Series only)

 

±2000 mV

 

(mV 600 Series only)

 

-9.9 to 120.0 °C

 

 

 

 

Resolution

0.01 pH

(pH 500 Series only)

 

1 mV

(mV 600 Series only)

 

0.1 °C

 

 

 

 

 

Accuracy

±0.02 pH

(pH 500 Series only)

(@20°C/68°F)

±2 mV

(mV 600 Series only)

 

±0.5 °C

 

 

 

 

 

Typical EMC Deviation

±0.2 pH

(pH 500 Series only)

 

±10 mV

(mV 600 Series only)

 

±0.5 °C

 

 

 

 

 

 

Installation Category

II

 

 

 

 

Power Supply

230 ±10% VAC or 115 ±10% VAC, 50/60 Hz

 

 

 

 

Power Consumption

15 VA

 

 

 

 

Over Current Protection

400 mA 250V FAST FUSE

 

 

 

Max.Oscillation Frequency 4 MHz

 

 

 

 

Relays 1 and 2

SPDT contact outputs, 5A - 250 VAC, 5A - 30 VDC

 

(resistive load)

 

 

Fuse protected: 5A, 250V FUSE

 

 

Alarm Relay

SPDT contact output, 5A - 250 VAC, 5A - 30 VDC

 

(resistive load)

 

 

Fuse protected: 5A, 250V FUSE

 

 

Environment

0-50 °C; max 85% R.H. non-condensing

 

 

 

Enclosure

single case ½ DIN

 

 

 

Weight

approximately 1.6 kg. (3.5 lb.)

 

 

 

 

8

Hanna Instruments PH 500 User Manual

INSTALLATION

pH 500 and mV 600 offer a multitude of possibilities, from single and dual setpoints to ON/OFF or proportional dosage, isolated outputs with user-selectable zoom, bi-directional RS232, recorder outputs in mAmps and volts.

In addition, pH 500 and mV 600 are both equipped with the exclusive differential input.

In a system with poor grounding, it is possible to have a ground current flowing through the reference junction. This can cause a rapid degradation of the electrode. The Hanna differential input reduces the likelihood of ground loops.

See the diagram for a recommended installation.

9

• Power Supply: Connect a 3-wire power cable to the terminal strip, while paying attention

to the correct line (L), earth (PE) and neu-

tral (N) terminal connections. Power: 115VAC - 100 mA / 230VAC - 50 mA

Line Contact: fused inside 400 mA.

PE must be connected to ground; leakage current 1mA.

Electrode: Connect the pH or ORP electrode to the BNC socket (#10 at page 7).

To benefit from the differential input, connect the proper electrode wire (if available) or a cable with a potential matching pin (grounding

bar) to the relevant terminal (#9 at page 7).

Note When it is not possible to immerse the Potential Matching Pin together with the pH electrode in the solution, disable the differential input by connecting the Connection for Potential Matching Pin (#9 at page 7) with the Connection for Electrode Reference (#8 at page 7) with a jumper wire.

Pt 100 Terminals: these contacts (#7 at page 7) connect the Pt 100 temperature sensor for automatic temperature compensation of pH measurement. In the case of shielded wire, connect the shield to pin 4.

In the case of a 2-wire sensor con-

nect the Pt 100 to pins 1 and 3, and short pins 2 and 3 with a jumper wire.

If the Pt 100 has more than 2 wires, connect the two wires of one end to pins 2 and 3 (pin 2 is an

auxiliary input to compensate for the cable resistance) and one wire

from the other end to pin 1. Leave

the fourth wire unconnected, if present.

• Power Supply Output: these terminals provide +5V and -5V DC signals to supply power to amplified electrodes.

Note All cables connected to rear panel should end with cable lugs.

10

SETUP MODE

pH 500 and mV 600 offer a multitude of possibilities from ON/OFF or proportional dosage to analog recorder output and from alarm to selftest features.

The Setup Mode allows the user to set all needed characteristics of the meter.

The setup mode is entered by pressing SETUP and entering the password when the device is in idle or control mode.

Generally speaking, if the password is not inserted the user can only view the setup parameters (except for password) without modifying them (and the device remains in control mode). An exception is certain setup items, or flags, which can activate special tasks when set and confirmed.

Each setup parameter (or setup item) is assigned a twodigit setup code which is entered and displayed on the secondary LCD.

The setup codes can be selected after password and CFM are pressed. When CFM is pressed, the current setup item is saved on EEPROM and the following item is displayed. Whenever LCD is pressed, the

device reverts back to control mode. The same is true when

CFM is pressed on the last setup item.

The possible transitions in setup mode are the following:

ENTERING THE PASSWORD

Press SETUP to enter the setup mode. The LCD will display “0000” on the upper part and “PAS” on the lower. The first digit of the upper part of the LCD will blink.

Enter the first value of the pass-

word by the or keys.

11

• Then confirm the displayed digit withand move to the next one.

• When the whole password has been inserted, press CFM to confirm it.

Note The default password is set at “0000”.

• The LCD will display “SET” on the upper part and “c.00” on the lower, allowing the user to edit setup parameters (see table below).

Enter the code of the parameter you want to set, using the arrow keys as per the password procedure above (e.g.41).

Confirm the code by pressing CFM and the default or the previously memorized value will be displayed with the first digit blinking.

Note When the password is not inserted or a wrong password is confirmed, the display will only show the previously memorized value, without blinking (read only mode). In this case, the value cannot be set. Press LCD and start again.

Enter the desired value using the arrow keys and then press CFM.

12

• Afterconfirmation,theselectedparameter is displayed. The user can scroll throughtheparametersbypressingCFM.

In order to directly set another parameter, press SETUP again and enter the code or scroll to it by pressing CFM.

The following table lists the setup codes along with the description of the specific setup items, their valid values and whether password is required to view that item (“PW” column):

Code

Valid Values

Default

PW

 

 

 

 

 

00

Factory ID

0 to 9999

0000

no

 

 

 

 

 

01

Process ID

0 to 9999

0000

no

 

 

 

 

 

02

Control enable/disable

0: C.M. disabled

0

no

 

 

1: C.M. enabled

 

 

 

 

 

 

 

11

Relay 1 mode

0: disabled

0

no

 

(M1)

1: ON-OFF high setpoint

 

 

2:ON-OFF low setpoint

3:Proportional, high setpoint

4:Proportional, low setpoint

12

Relay 1 setpoint

0.00 to 14.00 pH

8.00 pH

no

 

(S1)

-2000 to 2000 mV

500 mV

 

 

 

 

 

 

13

Relay 1 hysteresis

0.00 to 14.00 pH

1 pH

no

 

(H1)

0 to 4000 mV

50 mV

 

 

 

 

 

 

14

Relay 1 deviation

0.50 to 14.00 pH

1 pH

no

 

(D1)

25 to 4000 mV

50 mV

 

 

 

 

 

 

21*

Relay 2 mode (M2)

same as relay 1

0

no

 

 

 

 

 

22*

Relay 2 setpoint (S2)

0.00 to 14.00 pH

6.00 pH

no

 

 

-2000 to 2000 mV

-500 mV

 

 

 

 

 

 

23*

Relay 2 hysteresis (H2)

0.00 to 14.00 pH

1 pH

no

 

 

0 to 4000 mV

50 mV

 

 

 

 

 

 

24*

Relay 2 deviation (D2)

0.50 to 14.00 pH

1 pH

no

 

 

25 to 4000 mV

50 mV

 

* Available only in models with two relays

13

Code

Valid Values

Default

PW

 

 

 

 

30 Relay 3 high alarm (HA)

0.00 to 14.00 pH

9.00 pH

no

 

 

-2000 to 2000 mV

600 mV

 

 

 

HA>LA, HA>S1 or HA>S2

 

 

 

 

 

 

 

31

Relay 3 low alarm (LA)

0.00 to 14.00 pH

5.00 pH

no

 

 

-2000 to 2000 mV

-600 mV

 

 

 

LA<HA, LA<S1 or LA<S2

 

 

 

 

 

 

 

32

Proportional control

1 to 30 min

5

no

 

mode period

 

 

 

 

 

 

 

33 Maximum relay ON time

10 to 9999 min

60

no

 

(after which an alarm mode is entered)

 

 

 

 

 

 

 

40

Analog output selection

0: 0-1mA

2

no

 

 

1: 0-20 mA

 

 

 

 

2: 4-20 mA

 

 

 

 

3: 0-5 VDC

 

 

 

 

4: 1-5 VDC

 

 

 

 

5: 0-10 VDC

 

 

 

 

 

 

 

41

Analog output

0.00 to 13.00 pH

0.00 pH

no

 

lower limit

-2000 to 2000 mV

-2000 mV

 

 

(O_VARMIN)

(O_VARMIN< O_VARMAX - (1.00pH or 50mV))

 

 

 

 

 

42

Analog output

1.00 to 14.00 pH

14.00 pH

no

 

upper limit

-2000 to 2000 mV

2000 mV

 

 

(O_VARMAX)

(O_VARMIN< O_VARMAX - (1.00pH or 50mV))

 

 

 

 

 

60

Current day

01 to 31

from RTC

no

 

 

 

 

 

61

Current month

01 to 12

from RTC

no

 

 

 

 

 

62

Current year

1997 to 9999

from RTC

no

 

 

 

 

 

63

Current time

00:00 to 23:59

from RTC

no

 

 

 

 

 

71

Baud rate

1200, 2400, 4800, 9600

4800

no

 

 

 

 

 

90

Display selftest

0: off

0

yes

 

1: on

 

 

 

 

 

 

 

 

91

Keyboard selftest

0: off

0

yes

 

 

1: on

 

 

 

 

 

 

 

14

Code

Valid Values

Default

PW

 

 

 

 

 

92

EEPROM selftest

0: off

0

yes

 

 

1: on

 

 

 

 

 

 

 

93

Relays and LEDs selftest

0: off

0

yes

 

 

1: on

 

 

 

 

 

 

 

94

Watchdog selftest

0: off

0

yes

 

 

1: on

 

 

 

 

 

 

 

99

Unlock password

0000 to 9999

0000

yes

Note The process controller automatically checks to ensure that the entered data matches other related variables. If a wrong configuration is entered, “WRONG” blinks on the LCD to prompt the user. The correct configurations are the following:

If M1=/ 0 then S1<HA, S1>LA; If M2=/ 0 then S2<HA, S2>LA; If M1= 1 then S1-H1>LA;

If M1= 2 then S1+H1<HA; If M1= 3 then S1+D1<HA; If M1= 4 then S1-D1>LA; If M2= 1 then S2-H2>LA; If M2= 2 then S2+H2<HA; If M2= 3 then S2+D2<HA; If M2= 4 then S2-D2>LA;

If M1= 1 and M2 = 2

then S1-H1>S2+H2, S2>LA, HA>S1;

If M1 = 2 and M2 = 1

then S2-H2>S1+H1, S1>LA, HA>S2;

If M1 = 3 and M2 = 2

then S1>S2+H2, S2>LA, HA>S1+D1;

If M1 = 2 and M2 = 3

then S1+H1<S2, S1>LA, HA>S2+D2;

If M1 = 4 and M2 = 1

then S1<S2–H2, S1–D1>LA, HA>S2;

If M1 = 1 and M2 = 4

then S1–H1>S2, S2–D2>LA, HA>S1; If M1 = 3 and M2 = 4

15

then S1>S2, S2–D2>LA, HA>S1+D1;

If M1 = 4 and M2 = 3

then S2>S1, S1–D1>LA, HA>S2+D2;

where the minimum deviation (D1 or D2) is 0.5 pH (for pH 500) or 25 mV (for mV 600).

Note The password cannot be viewed when SETUP is pressed without entering the original password first. The default password is set at “0000”. In the event that the user forgets the password, this can be reset to “0000” by pressing and holding CFM and then pressing LCD and CAL DATA at the same time when the pH controller is in normal operating mode (idle or control with measurement displaying).

Note When a wrong setup value is confirmed, the pH controller does not skip to the next setup item but remains in the current item displaying a flash-

ing “WRONG” indicator until the pa-

rameter value is changed by the user (the same is also true for the setup code selection). In some circumstances, user cannot succeed in setting a parameter to a desired value if the related parameters are not changed beforehand; e.g. to set a pH high setpoint to 10.00 the high alarm must be set to a value greater than pH 10.00 first.

Note For code numbers 40, 41, 42, the output is related to pH or mV units depending on the model (pH process meters or mV process meters).

16

CONTROL MODE

The control mode is the normal operational mode for these meters. During control mode pH 500 and mV 600 fulfill the following main tasks:

convert information from pH/ORP and temperature inputs to digital values;

control relays and generate the analog outputs as determined by the setup configuration, display alarm condition;

RS232 management.

In addition, pH 500 and mV 600 can log working data through RS232 connection. This data includes:

pH, mV and oC measured values;

last calibration data;

setup configuration (also from PC).

The status of the meter is shown by the LED’s on the right

 

STATUS

 

LEDs

 

Control

Alarm

Alarm LED (green)

RelayLED(yellow)

Red LED

 

 

 

 

 

OFF

----

ON

OFF

ON

 

 

 

 

 

ON

OFF

ON

ON or OFF

OFF

 

 

 

 

 

ON

ON

OFF

ON or OFF

Blinking

 

 

 

 

 

Meter exits control mode by pressing SETUP or CAL and confirming the password. Note that

this command generates a temporary exit. To deactivate the

control mode definitively, set CONTROL ENABLE to “0” (item # 02).

RELAY MODES

Once enabled, the relays 1 and 2 can be used in four different modes:

1)ON/OFF, high setpoint (acid dosage);

2)ON/OFF, low setpoint (base dosage);

3)proportional, low setpoint (base dosage, if available);

4)proportional, high setpoint (acid dosage, if available).

17

An upper boundary is imposed for acid/base dosage time when relays are energized continuously, i.e. when relay works in ON/OFF mode or in proportional mode but in the latter case only if the relay is always ON. This parameter can be set through setup procedure. When the maximum boundary is reached, an alarm is generated; device stays in alarm condition until relay is de-energized.

ON/OFF CONTROL MODE

Either for mode 1 or 2 (base or acid dosage) the user has to define the following values through setup:

relay setpoint (pH/mV value);

relay hysteresis (pH/mV value).

Connect your device to the COM and NO (Normally Open) or NC (Normally Closed) terminals.

The ON relay state occurs when relay is energized (NO and COM connected, NC and COM disconnected).

The OFF relay state occurs when relay is de-energized (NO and COM disconnected, NC and COM connected).

The following graphs show relay states along with pH measured value (similar graph can be derived for mV control).

As shown below, a high setpoint relay is activated when the measured pH exceeds the setpoint and is deactivated when it is below the setpoint value minus hysteresis.

ON

 

 

OFF

 

 

Setpoint –

Setpoint

14

Hysteresis

 

 

Such a behavior is suitable to control an acid dosing pump. A low setpoint relay as can be seen from the following graphs is energized when the pH value is below the setpoint and is de-energized when the pH value is above the sum of setpoint and the hysteresis. The low setpoint relay may be used to control an alkaline dosing pump.

18

ON

 

 

OFF

 

 

Setpoint

Setpoint +

14

 

Hysteresis

 

PROPORTIONAL CONTROL MODE

The user can vary three different parameters, i.e. the setpoint (S1 or S2), the deviation (D1 or D2) and the proportional control mode period Tc from 1 to 30 minutes. Duration of the activated control is directly proportional to the error value (Duty Cycle Control Mode): as the measurement approaches setpoint, the ON period diminishes.

The following graph describes the pH process controller behavior. Similar graph may apply to the mV controller.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

t0

t0+Tc

 

t0+2Tc

t0+3Tc

During proportional control the process controller calculates the relay activation time at certain moments t0, t0+Tc, t0+2Tc etc. The ON interval (the shaded areas) is then proportional to the error amplitude.

For example with S1 representing High Setpoint Setpoint (S1) = 7.00 pH

Deviation (D1) = 1.00 pH Tc = 1 minute

If measurement > 8.00 pH, then

ON all the time.

If measurement = 7.60 pH, then

ON for 36 seconds

 

OFF for 24 seconds.

If measurement = 7.10 pH, then

ON for 6 seconds

 

OFF for 54 seconds.

The number of strokes per minute of the pump can be changed only by means of the pump’s command.

Referring to the following diagram (low setpoint) the relay is:

ALWAYS ON if pH < setpoint-deviation;

ON proportionally to the error

if setpoint - deviation < pH < setpoint

19

• ALWAYS OFF if pH > setpoint;

ON

Low setpoint mode

OFF

0 alarm

Setpoint–

Setpoint

14

Deviation

Using a similar format, the second relay may be set up according to the diagram below.

High setpoint mode

ON

 

 

 

 

OFF

 

 

 

 

0

Setpoint

Setpoint +

alarm

14

 

 

Deviation

 

 

ALARM RELAY

The alarm relay functions in the following manner:

FS•C = NO (Normally Open)

Energized Relay

COM

FS•O = NC (Normally Closed)

De-energized Relay

During alarm condition, the relay is de-energized. When not in alarm condition, the relay is energized.

Example:

High alarm set at 10 pH

 

 

 

 

 

 

 

 

Low alarm set at 4 pH

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Note If the power supply is interrupted, the relay is de-energized as if in alarm condition to alert the operator.

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