Measuring and controlling ozone levels in water treatment using Redox/ORP method

Measuring and controlling Ozone levels in water?

The Ozone dosing of water is measured in millivolt terms and is expressed as the REDOX or ORP level (Reduction /Oxidation potential) of the water. Normal pond water will have a REDOX level of around 200mv or less. Sterile water has a REDOX level of around 700mv. Some Ozone generators are designed to automatically regulate the ozone dosing to keep the REDOX level at a preset level, normally around 350mv – 380mv in a healthy aquatic environment, so that the water is not sterile or anything like, since it could not then support life.

What is a Redox reaction?

A chemical reaction in which electrons are removed from one atom (which is thereby oxidised) and added to another (which is thereby reduced). The movement of electrons is then measured on a millivolt scale.

Aquazone Model 61 mV ORP/Redox CONTROLLER.

GENERAL DESCRIPTION.

The Aquazone Model 61mV is a single-channel, micro-processor based mV controller.

The signal form the mV electrode is optically isolated before it is sent to the micro-processor behind the front panel. The micro-processor controls the all the output- as well as programming- and set-up functions.

This arrangement eliminates ground-loop and signal feed-back errors.

Three push-buttons on the front panel allow for the easy programming of the controller.

The mV reading and set-point are displayed on a LCD screen with a build-in backlight controlled by a light-sensor.

A proportional pulse output is supplied for the control of solenoid-driven dosing pumps. The maximum pulse rate can be set from 50-180 pulses/minute.

“OUT1” is a relay output that can be set as an “On/Off” output or as a “Proportional Time” output to control a motor driven dosing pump.

“DOSE” is used to dose chemical to increase the mV reading.

“BLEED” is used to decrease the mV reading.

STANDARD SPECIFICATIONS:

Power requirement: 200-240V, AC only.

Power consumption:     5 VA

Instrument fuse:       250mA

Output fuse:           5A

INTERLOCK: Used for remotely switching controller on or off.

Range:            -1000 to +1000 mV.

Accuracy:              +- 10 mV (After calibration).

Display:            2 x 16 characters LCD module with backlight.

The backlight options are: “Always ON”.

   “Always OFF”

   “Ambient”.

µProcessor: Microchip PIC18F4525.

Software: Version: HJM632mV and up.

mV input:              BNC connector.

mV pre-amplifier:      PCB mount, epoxy encapsulated for moisture protection.

Pulse 1: Proportional pulse output for dosing pump.

Maximum pulse rate: 50-180 pulses/minute adjustable

Pulse 1 light: Yellow LED.

Out 1: On/ Off or proportional time output.

N/O relay contact, 5A into resistive load.

Potential free or 220Vac

Suppressed with 47 R and 0.033 μF.

                    (Will supply 2,5mA current when the relay is off).

Out1 light: Red LED.

Probe Fault light: NOT USED.

RUN light:             Flashing green LED. Indicates that the µProcessor is running.

UP/DOWN buttons: Used to select software options.

ENTER/Set button: Used to set software options.

Enclosure:           Polycarbonate, light gray color with clear hinged lid.           

Protection: IP 545.  Size: 184 x 160 x 140 mm.

   Mounting holes distance: 180mm.

Protection:            IP 65.

Size:                  184 x 180 x 140 mm.

Front label:           Anodised aluminium, green on silver.

4-20mA output Isolated. Range: -100mV to +1000mV, Proportional to mV reading.

or as a 4-20mA control signal.

                      Maximum load 600 Ohm.

                      Accuracy: +- 0.05mA            

                  

STANDARD FACTORY DEFAULT SETTINGS:

Setpoint 1:  +500mV

Control:   Dose

Maximum Pulse Rate 1:  150 pulses/Minute Maximum.

Relay Output Function:   Proportional Time output.

Relay Period:   90 seconds

Relay minimum ON time: 15 seconds

Hysteresis:   0,5 pH

Pulse Maximum Range:   1 pH

Backlight:   Ambient

4-20mA Output:   -1000mV to +1000mV recording signal.

INSTALLATION.

 

WALL MOUNTING.

The Model 61mV controller can be mounted by using the 2 mounting brackets, or it can be mounted

on a DIN rail using DIN rail clips (optional extra).

INSTALLATION.

Before installing the mV controller, a bit of thought has to be given to the position where the unit is to be installed.

AVOID: a) Splashing or dripping of liquids against the control panel.

  1. b) Mounting the controller close to steam traps or hot water trenches.
  2.       c) Installation in highly corrosive environment, i.e. chlorine fumes or corrosive

  gasses and liquids.

  1. d) Installation in places where strong mechanical vibrations are present.
  2. e) Running mV probe cable next to other cables, motors, fans or generators.

DO: a) Install instrument under cover where possible.

  1. b) Mount instrument in dry and clean position with easy access.
  2. c) Run mV cable separately from other cables.
  3. d) Install the instrument as close as possible to the probe.

1) Connect all outputs first.

2) Connect 220V supply to mains input terminals. This supply should be earth-leakage protected

    and MUST include an earth wire.

   Under no circumstances must the instrument be connected to a two-wire supply only.

IMPORTANT NOTE:

    Please ensure that the Mains input wires are connected to the correct terminals.

    Failure to do so will render the fuse protection inoperative!

3) Connect the mV probe. REMOVE THE PROTECTIVE CAP.

TERMINAL CONNECTIONS:

4-20 mA SIGNAL.

The isolated 4-20mA signal can be used as a recording signal.

It operates over a -1000 to +1000 mV range.

8 = -, 4-20 mA output.

9 = +, 4-20 mA output.

220V INPUT:

10 = E (Earth) input.    (linked to 16 = E (Earth) output)

11 = N (Neutral) input. (linked to 17 = N (Neutral) output)

12 = L (Live) input.

 

ON/OFF SWITCH.

Used for remotely switching controller on or off. Must be linked if not used!

13 + 14 = ON/OFF SWITCH.

220V OUTPUT:

15 = L (Live) output.

16 = E (Earth) output.    (linked to 10 = E (Earth) input)

17 = N (Neutral) output. (linked to 11 = N (Neutral) input)

 

OUT1 RELAY:

18 = N/O, Relay output (L2).

19 = C, Relay common (L1). Link to 15 for 220V output

 

PROPORTIONAL PULSE OUTPUT:

43 + 44 = Pulse1 relay output.