Hofmann PMH-2 User manual

DIGITAL
pH / ORP / mV
CONTROLLER
PMH-2
USERS GUIDE
PMH-2 Instruction manual PAGE 1

TABLE OF CONTENTS
SPECIFICATIONS . . . . . . . . . . . . . . . . 3
INTRODUCTION . . . . . . . . . . . . . . . . . 5
Normal dosing (nor) 6
Normal Proportional dosing (no.P) 6
Adaptive proportional dosing. (Ad.P) 6
INSTALLATION . . . . . . . . . . . . . . . . . 9
Instrument . . . . . . . . . . . . . . . . . . . 9
Wiring of the PMH-2 10
Signal output 11
Electrodes 11
Starting up the Instrument. 11
CONFIGURATION . . . . . . . . . . . . . . . . 12
Looking at menus and values . . . . . . . . . 12
Default values for the PMH-2 instrument 13
Saving Values in Configuration. . . . . . . . . 14
OPERATION . . . . . . . . . . . . . . . . . . . 19
Initial check of the PMH-2. . . . . . . . . . . 19
Calibrating the PMH-2 with a simulator. . . . . 19
Selecting Mode of Operation. . . . . . . . . . 21
PMH-2 and Swimming Pools. . . . . . . . . . 27
WARRANTY . . . . . . . . . . . . . . . . . . . . 28
PAGE 2 PMH-2 Instruction manual

SPECIFICATIONS
Range: 0 - 14pH, 0.01 pH resolution
0 - 1999mV with 1mV resolution.
Display: 3 1/2 digit LCD displays.
Indicators: LED lights indicate set point operation, pulse, flow,
configuration and calibration status.
Calibration: All calibration parameters are programmed into non-
volatile memory.
Electrode: BNC, external of housing.
Temperature: Manual compensation selected in the configuration
menu if in pH mode. Temperature range from 0 to
100oC. Automatic compensation possible with a
TP-100 electrode connected.
Signal output: 4-20mA software configuration over range 0-14pH or
0-1000mV. Current output fully isolated. Maximum
termination impedance for 20mA is 1000 Ohms.
Control range: Set point range 0pH to 14pH or 0 to +1000mV
Pulsed output: Selected for Relay1 through setup program. Pulse
width adjusts automatically to suit dosing require-
ments. On time varies from continuous to minimum 1
second. Pulse interval increases / decreases to fur-
ther fine-tune a dosing cycle.
PMH-2 Instruction manual PAGE 3

Relay 1: 240 VAC, 5 Amps max. Resistive load. 3 terminals
provide earth, neutral and switched active. 5A fuse
protects instrument and relay output.
Relay 2 / Alarm: Potential free contacts.
Power: 240VAC 50Hz 7.5VA max. Hardwired with screw
terminals located under sub panel. 3 way terminal
providing 240VAC (A, N, E) located next to potential
free contacts allows for easy wiring of this terminal.
Housing: Fully sealed construction with hinged clear acrylic
front cover. IP55 specifications.
Dimensions: 166mm x 160mm x 105mm.
PAGE 4 PMH-2 Instruction manual

INTRODUCTION
The new PMH-2 controller features a simple and safe way for all
configuration and calibration procedures. All programmed parameters are
stored in non-volatile memory and are not lost if the instrument looses
power.
You use the ‘rotary encoder knob’ to scroll through setup menus and
dial up/down numbers when prompted to enter values for relay or alarm
setpoints, current signal low and high points etc.
The desired value is selected and saved by pushing the rotary encoder
knob. The rotary encoder only becomes active if invoked through the
instrument configuration program. This feature avoids setpoints or cali-
bration values being changed inadvertently.
The PMH-2 features 2 output relays. Relay1 has switched 240VAC.
This output can be configured for up/down dosing in on/off mode, propor-
tional dosing or adaptive proportional dosing. Relay2 has potential free
contacts with up/down dosing or configured as alarm.
FIG 1 PMH-2 CONTROLLER
PMH-2 Instruction manual PAGE 5

LED’s show the operational status of the instrument or setup program
currently available. Pushing the encoder prepares for performing configu-
rations or calibrations. Rotating the encoder clockwise and pushing again
enters the configuration menu to set up the instrument. Rotating the
encoder anticlockwise and pushing enters the calibration menu. You scroll
through menus with the encoder knob and once a menu is selected values
are increased or decreased by rotating the encoder knob clock- or
anti-clockwise. The desired value is selected and saved with pushing the
encoder until the “SAVE” LED flashes two times. (See configuration)
The large LCD display shows either signal input, configuration or
calibration values such as set point or high/low alarm as selected by an
operator.
FThe rotary encoder only becomes active if invoked through the instrument
configuration program. This feature avoids setpoint or calibration values
being changed inadvertently.
Three modes of set point control are possible with Relay1:
Normal dosing (nor)
This is the normal dosing mode with simple on/off operation of the
output relay. Up or down dosing is possible with normal dosing.
Normal Proportional dosing (no.P)
The relay output starts to pulse with a shortening of the ON cycle and
a lengthening of the OFF cycle as the pH / mV moves toward the setpoint.
The behaviour of the pulse mode can be modified by setting a “gradient”
from 10 to 100. (See Fig. 6) Minimum default pulse ON time when reaching
the set point is 2 seconds. This can be changed from 1 to 9 seconds to
suit all applications. These configurations only becomes available if no.P
is selected. Up or down dosing is possible with normal proportional dosing.
Adaptive proportional dosing. (Ad.P)
The relay output of the PMH-2 instrument is controlled through a
complex algorithm that continuously monitors the difference between
actual pH / mV and set point. The output starts to pulse and varies the
PAGE 6 PMH-2 Instruction manual

ON/OFF cycle as the input value approaches the set point value. The
ON/OFF cycle however is also adjusted from a ‘correction factor’, which
in turn is governed by the history of a previous dosing cycle. This makes
for a fully dynamic dosing control, which adapts for widely varying dosing
conditions. (See Fig.7)
Dosing for an excessive period of time without a corresponding increase
in pH is recognized as a possible failure. The output begins to pulse,
preventing overdosing. The pulse output exhibits a very wide duty cycle.
The ON and OFF times are both dynamic, both varying from 1 to 60
seconds. Up or down dosing is possible with “Adaptive proportional
Dosing”. ! If using AdP the second relay must be configured as alarm !
FThe PMH-2 program prevents gross overdosing in the event of a process
upset or electrode failure. (Adaptive mode only)
FIG 2 LED's show different conditions.
PMH-2 Instruction manual PAGE 7

Temperature compensation (pH mode only) is set for 20oC by default.
This can be changed in the configuration program from 0 to 100oC.
A PT-100 temperature electrode connected to the terminals enables the
option for automatic compensation.
The PMH-2 features an alarm relay with potential free contacts. Low
and high alarm points are set in the configuration menu. ALARM/Relay2
can also be configured to perform as a second setpoint relay in either up
or down mode.
The flow switch input is configured to operate as N/O or N/C. (normally
open or normally closed) If no flow is detected relay 1 and relay 2 are
locked out and the relay’s LED flash. The flow LED indicates this condition.
The inherent accuracy and range configuration of the 4-20mA constant
current output together with full electrical isolation make it possible to
interface into a microprocessor, logic controller or data logger to further
expand the combination of installations with the PMH-2.
PAGE 8 PMH-2 Instruction manual

INSTALLATION
Instrument
Select a position for the controller to be mounted on a wall, not facing into
direct sunlight and protected from the weather elements as much as possible.
The PMH-2 should be installed near the treatment plant. Maximum length of
the co-axial cable used should not exceed 10 metres because of the very high
input impedance characteristic of a pH electrode.
The metal electrodes used for redox measurements are of much lower
resistance and longer coaxial cables can be used without any special
precautions.
Insert a round headed screw into the panel where the instrument is to
be attached. This screw determines the centre of the instrument location.
(Fig.3) 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.
FDo not drill any holes into the enclosure to install the controller.
FIG 3 Attaching the DPH-4 to a wall
PMH-2 Instruction manual PAGE 9

Wiring of the PMH-2
It is imperative that all connections are wired through the cable gland
and the transparent lid is always tight to ensure that no corrosive liquids
inadvertently splash into the instrument.
The 3 terminals for relay1 provide an earth, neutral and switched
240VAC (active) . A metering pump, solenoid valve or other device
requiring 240V can be connected.
A suppression capacitor is already connected to filter electrical spikes
caused by switching solenoid valves.
The ALARM/relay2 terminal has potential free contacts. (N/O C N/C)
You need to determine the N/O or N/C of a flow switch when connecting
for proper configuration later on. Polarity does not matter when wiring a
flow switch.
FThe Set point relay terminals connect to earth, neutral and switched active
240V. (240VAC is supplied to these terminals when activated by the set point.)
FIG 4 Terminal layout for the PMH-2
PAGE 10 PMH-2 Instruction manual

Signal output
The 4-20 mA signal current output can be used for event recording or
to expand the control facilities for additional relay contacts. This output
can be wired directly to a computer interface without causing earth loop
problems. Correct polarity wiring is essential.
The current signal can also be configured to drive a metering pump with
a signal input. (See Fig. 9)
FCorrect polarity has to be observed when connecting the 4-20mA signal
output.
Electrodes
The co-axial cable used to connect the electrode to the PMH-2 must be
of the type supplied with a carbon sleeve between the centre core and
shield as any standard co-axial cable will cause a very erratic reading. An
impedance converter must be used if the location between electrode and
controller exceeds 10 meters. Special consideration also must be given
when placing an electrode in a treatment bath or pool. The point of injection
of neutralising agent and placement of the electrode (distance between
them) largely determines the dosing characteristics of the PMH-2.
FOnly use special co-axial cable to connect a pH electrode to the PMH-2.
Starting up the Instrument.
After you have installed the instrument and checked all the wiring and
connections open the isolation valves to the sensor to allow water flow
across it. Plug the power cord into the supply and switch on the PMH-2.
The “RUN/CONFIG” LED will light up green and the digital display shows
the measured input value.
FTo quickly change the setpoint push and hold down the encoder until the
green LED flashes and the present setpoint is displayed. Release and dial
a new setpoint. Push again until the SAVE LED flashes two times.
PMH-2 Instruction manual PAGE 11

CONFIGURATION
Looking at menus and values without changing or saving.
The PMH-2 is now in ‘RUN’ mode and processes the mV signal, output
and alarm relays and the signal output. This condition is indicated with the
green ‘RUN/CONFIG’ light. Turning the encoder knob has no effect.
Now push the encoder knob. The LED changes to flashing red. Turn
the knob clockwise. The LED changes to steady red and the display
shows CnF. Now push to move to the first configuration mode. The
display shows UP. Slowly rotate the knob to sweep through all the modes:
Dosing up / down,
Setpoint,
Dosing mode for relay1
Temperature configuration (with pH selected only)
Low / high alarm or dosing mode for relay2
Flow switch
4-20mA Signal
End
The corresponding LED lights up for each of the above position to show
which mode is indicated with the LCD display.
The next step shows End, here you can exit back to ‘RUN’ by pushing
the encoder or continue to step clock-wise or anti-clockwise to look at the
configurations again. There is no need to exit manually as the PMH-2
automatically returns to ‘RUN’ after 2 minutes if left anywhere in the
configuration or calibration menu.
FThe PMH-2 automatically returns to ‘RUN’ after 2 minutes if left anywhere
in the configuration or calibration menu.
If a program mode is entered inadvertently by pushing the encoder,
simply push again until the ‘SAVE’ LED flashes. The same mode or value
is retained as was previously programmed.
PAGE 12 PMH-2 Instruction manual

Default values for the PMH-2 instrument
The PMH-2 is shipped with default values programmed in non-volatile
memory.
mV MODE
Dosing = UP UP
Setpoint = 700 700
Dosing Mode = normal dosing no.d
Low Alarm mV = 200 200
High Alarm mV = 1000 1000
Flow Switch = Normally open OP
4-20mA signal output mode = normal nor
4mA = 000mV 000
20mA = 1000mV 1000
pH MODE
Dosing = UP UP
Setpoint = 7.00 7.00
Dosing Mode = normal dosing no.d
Temperature Compensation
Manual (+20.0oC) S.oC (+20.0)
Low Alarm pH = 2.00 2.00
High Alarm pH = 10.00 10.00
Flow Switch = Normally open OP
4-20mA signal output mode = normal nor
4mA = 0.00pH 0.00
20mA = 14.00pH 14.00
Of course all values can be customised through the configuration setup.
Entered values are stored in non-volatile memory and are not lost through
power failure.
PMH-2 Instruction manual PAGE 13

Changing and Saving Values in Configuration.
This chapter only explains the different selections available and how to
change modes or values. Look up “OPERATION” for more details of when
to use different settings.
General:
Table 1 (pH) and Table 2 (mV) is an overall diagram of all the variables
that can be changed in configuration. The LCD display shows a mode or
value and the appropriate LED lights up to show the position presently
showing. Pushing the encoder prepares to change this value. This is
indicated by the LED flashing. To save a change push until the yellow
“SAVE” LED flashes twice. The change is now saved in non-volatile
memory and will be used by the PMH-2.
This manual from now on will say:
Pushing the encoder: ‘PUSH’
Pushing the encoder until the save LED flashes twice: ‘SAVE’
Clockwise direction of the encoder knob: Rotate ‘CW’
Counter-clockwise direction of the encoder knob: Rotate ‘CCW’’
Either direction of the encoder: “Rotate’
FTo change large numbers quickly rotate the encoder in a “flicking” manner.
Dosing mode is selected for up [UP] or down [dn].
Setpoint is selected between 0.00 to 14.00pH or 000 to 1000mV
Next select the relay output mode. There are three options.
Normal dosing [no.d], Normal Proportional dosing [no.P] and
Adaptive Proportional dosing [Ad.P]
(pH only) Temperature compensation is selected manually in +oC mode.
‘PUSH’ and dial up the new temperature. Range is 0 to 100oC.
Connecting a PT100 temperature sensor enables the PMH-2 to use
automatic compensation. Select SoC for manual or AoC for auto com-
pensation. In AoC mode the actual temperature is displayed.
Exit without saving by rotating the encoder (Temp LED goes off) and then
‘PUSH’. Press ‘SAVE to accept automatic compensation.
PAGE 14 PMH-2 Instruction manual

The next menu sets Relay2 as alarm or up/down setpoint mode. The
LED shows green with up/down, red with alarm. Push and rotate to select
alarm, down or up. If alarm selected, push again to set the low alarm
setpoint. The LED now flashes slow. Low alarm range is from 0.00pH
(000mV) to high alarm. High alarm range is from low alarm to 14.00pH.
(1000mV) After saving down or up mode rotate to move to change the
setpoint. Default setpoint is set at pH 7.50 (750mV) for down mode,
pH 6.50 (650mV) for up mode.
Flow switch configuration mode is selected for normally open [OP] or
normally closed. [CL]
4-20mA output is configured for normal [nor] or setpoint [SP.] operation.
The pH / mV for 4mA and 20mA are selected in the next configuration. First
the 4mA LED flashes to allow entering and ‘SAVE’ pH / mV for 4mA. Repeat
this procedure for 20mA. 4mA range is from 0.00pH (000mV) to pH7.00
(500mV). 20mA range is from pH8.00 (600mV) to pH14.00 (1000 mV).
Only the 20mA slope is entered in mA Setpoint. Range for the mA slope
is 0.5 to 5.00pH (50 to 500 mV). 4mA always is setpoint. It is important to
note that dosing mode [UP, dn] is properly selected if SP. mode is used.
If additional changes are necessary rotate ‘CW’ or ‘CCW’ to return to
any of the above mentioned options. Only a single configuration change
can be made if necessary. There is no need to configure from beginning
to end.
FA single configuration change can be made if necessary. There is no need
to configure from beginning to end.
When all configurations are done step to the next menu [End] to exit.
‘PUSH’ returns to operating mode. The PMH-2 always returns to operating
mode after 2 minutes if left in configuration or calibration mode.
To only change the setpoint push and hold down the encoder until the
green LED flashes and the present setpoint is displayed. Release and dial
a new setpoint. Push again until the SAVE LED flashes two times.
PMH-2 Instruction manual PAGE 15

PAGE 16 PMH-2 Instruction manual

PMH-2 Instruction manual PAGE 17

Offset calibrations can be performed if the electrode signal is between
pH 6.00 and 8.00 or -50 and +250mVA mV. The message ‘ Err ‘ indicates
if pH / mV is out of range. If this is the case ‘PUSH’ twice, adjust pH / mV
for correct value and repeat offset calibration.
A slope calibration can be performed if the pH is lower than 5.5. or higher
than 8.5 or in mV mode between 280mV and 900mV. The message ‘ Err ‘
will show if this condition is not met. If this is the case PUSH twice, adjust
pH / mV for correct value and repeat mV calibration.
PAGE 18 PMH-2 Instruction manual

OPERATION
Initial check of the PMH-2.
After the instrument is properly installed, an electrode or simulator
connected and the power applied, the “RUN” LED will light up. The output
relay may latch depending on the signal input. Sweeping across the range
with a simulator will activate the relay and “RELAY OUTPUT” LED at the
programmed setpoint.
Calibrating the PMH-2 with a simulator.
The operator should be familiar with the different effects if OFFSET and
SLOPE calibrations are carried out. Offset adjustments increase or de-
crease the reading regardless of the absolute measured value. pH7 is a
prefixed iso-potential and increasing the slope always moves the reading
away from pH7. Readings below pH7 therefore decrease in the displayed
value. Readings above pH7 increase in the displayed value. (Fig.6)
OFFSET calibrations should be carried out first, however offset and
slope calibrations can be performed separately and need not be done
consecutively.
Set the simulator to pH 7.00‘
PUSH’ and ‘Rotate CCW’ to go to CAL. ‘PUSH’ turns on the offset LED.
‘PUSH’ again, the offset LED now flashes and the display shows “live” pH
FIG. 5 THE DIFFERENT EFFECTS OF OFFSET AND SLOPE.
PMH-2 Instruction manual PAGE 19

input. ‘Rotate’ until 7.00 shows on the display and ‘SAVE’. Offset is now
calibrated.
An offset calibration can only be performed if the pH is between 6.00
and 8.00. The display shows Err if a value outside these parameters is
present. ‘PUSH’ two times, the display shows “live” pH to allow the
operator to correct for a valid offset pH value. ‘PUSH’ now returns to the
offset calibration menu to repeat the procedure.
Rotate ‘CCW’ goes to End then ‘PUSH’ to exit. Rotate ‘CW’ proceeds
to the slope calibration.
SLOPE calibration.
Set the simulator lower than pH 5.50 or higher than pH 8.50‘
PUSH’ turns on the slope LED. ‘PUSH’ again, the slope LED now
flashes and the display shows “live” pH input. ‘Rotate’ until the correct
slope value shows on the display and ‘SAVE’. Slope is now calibrated.
An accurate slope calibration can only be performed if the pH is lower
than 5.50 or higher than 8.50 The display shows Err if a value inside these
parameters is present. ‘PUSH’ two times, the display then shows “live”
pH to allow the operator to correct for a valid pH value. ‘PUSH’ now returns
to the slope calibration menu to repeat the procedure.
Rotate ‘CCW’ two times goes to End then ‘PUSH’ to exit. Rotate ‘CW’
proceeds to mA calibrations. (See 4-20mA output)
Redox electrodes
Contrary to pH electrodes, redox (metal electrodes) do not exhibit
changes in slope or zero point. Nevertheless one may occasionally
experience wrong redox measurements, most frequently the cause being
a contaminated electrode. Cleaning and/or regeneration of the electrode
will cure the problem. It is very unusual to get wrong readings with redox
electrodes when using redox buffer solutions. The use of redox buffers
therefore is restricted to a simple function test of a redox electrode.
The mV offset and mV slope calibration modes of the PMH-2 are mainly
used to correct minor instrument offset or gain errors of the input section.
PAGE 20 PMH-2 Instruction manual