Hydro WQM-100 User manual
WQM-100
Water Quality Monitor
Instruction Manual
WQM-100 Rev. 8/25/2020
The information contained in this manual was current at the time of printing. The most current
versions of all Hydro Instruments manuals can be found on our website: www.hydroinstruments.com
1
Hydro Instruments
WQM-100 Water Quality Monitor
Table of Contents
I. General Information .................................................................................3
1. Important Operational Information
2. Important Handling Considerations
3. Electrode Lifespan
II. Installation ................................................................................................4
1. Sample Water Connection and Control
2. Sample Water Disposal Considerations
3. Sample Point Selection
4. Mounting the Electrodes
5. Wiring the Electrodes
6. Installation Inspection
III. Calibration and Programming .................................................................8
1. Conditioning
2. Programming the WQM-100
3. Programming Access
3. Operating the Keypad
IV. Explanation of Operation Mode Screens .............................................11
V. Explanation of Confi guration Mode Screens ......................................14
VI. Explanation of PID Control Mode Screens ..........................................18
VII. Maintenance & Cleaning ........................................................................20
1. Inlet Filter Screen
2. Flushing the Measurement Cell
3. Thermistor
4. pH Electrode
5. ORP Electrode
6. Conductivity Electrode
VIII. Troubleshooting .....................................................................................21
IX. Optional Data Logger .............................................................................24
Figures:
1. Sample Water Piping Examples ......................................................................5
2. Sample Point Sources .....................................................................................6
3. Installation Example ........................................................................................6
4. Example Mounting Gland, Quick-Disconnect Cap & Cable Assembly ............7
5. Operation Menu Flow Chart ............................................................................9
6. Hidden Confi guration & Live Data .................................................................10
7A. Confi guration Menus .....................................................................................12
7B. Confi guration Menus .....................................................................................13
8. Circuit Boards ................................................................................................27
9. Monitor Internal Wiring and Connections ......................................................28
Drawings:
Electrode Measurement Cell .........................................................................26
2
I. GENERAL INFORMATION
1. Important Operational Information
To increase the life expectancy, accuracy and response of the electrode adhere to the following
operational guidelines:
1. Keep the electrode wet. Allowing the electrode to dry out will lead to slow response, erroneous
readings and damage.
2. Clean the electrode regularly
• Take care when cleaning the electrode. Never use a brush or coarse surface for cleaning.
• To clean, simply rinse the electrode with water. Blot (do not rub) with a lint-free paper towel to
remove excess moisture.
• Specially formulated cleaning solutions can be used to clean the electrode too.
• Wiping the glass can produce a static charge which interferes with the electrodes ability to
read.
2. Important Handling Considerations
The electrodes are shipped in a cap containing a solution. The electrode should only be removed from
this solution when it is ready to be installed and used.
NOTE: If the electrode will be subject to infrequent use it should be stored in Storage Solution or in a
pH 4 buffer solution if Storage Solution is not available. Do not store the electrode in deionized (DI)
water as this will damage the electrode.
3. Electrode Lifespan
Just like any piece of equipment, electrodes need to be replaced from time to time as regular
maintenance. As sensors age they become less responsive. The off set and slope are metrics
by which to measure the electrodes functionality. Refer to Appendix A in this document for more
information.
The manufacturing lot number can be found on the label on the electrode. This information can be
used to determine the age of the electrode.
3
II. INSTALLATION
Refer to Figure 3 for this section.
1. Sample Water Connection and Control: The following are some considerations relating to the
sample water supply. The WQM-100 Water Quality Monitor requires a constant supply of sample water
at a controlled rate and pressure. Precautions should also be taken to ensure that the sample water
reaching the measurement cell is not altered as it passes through the sample water piping. Also, the
connection to the sample point should be made in such a way to avoid receiving air or sediment from
the pipe. Consider fi gure 4 when creating your sample water line
Flow: The sample water fl ow rate should be controlled at an ideal rate of 500 ml/minute (8 GPH).
A fl ow meter and rate control valve may be necessary to achieve and maintain this fl ow rate. This
can be installed upstream from the measurement cell.
Pressure: Where the sample point has a water pressure higher than 87 PSI (6 bar), a pressure-
reducing valve must be employed to deliver the sample water to the measurement cell. The sample
water entering the measurement cell should be at a pressure below 87 PSI (6 bar). If the sample
point pressure is too low, then it may be necessary to use a sample pump to deliver the sample water
to the measurement cell.
Other Considerations: It should be considered, that any biological growth inside the sample piping
system will have some adverse eff ects. This can cause the sample water reaching the measurement
cell to not be an accurate sample. For example, the ORP could change as the sample water passes
through the sample water piping system. For this reason, it may be necessary to periodically clean
the sample water piping system to prevent any biological growth or clear out residual chemical
buildup. Also, it is generally not recommended to use a fi lter in this piping system because as the fi lter
collects particles it can lead to inaccurate readings. However, in certain installations with signifi cant
amounts of solids in the sample water (particularly iron and manganese) the use of sample water
fi lters may be necessary.
2. Sample Water Disposal Considerations: If no reagent and/or pH buff er chemical is being
injected, then the disposal of the water departing the measurement cell is usually not a signifi cant
concern. However, if some reagent and/or pH buff er chemicals are being injected, then all applicable
regulations should be considered before making the decision of how and where to dispose of
the wastewater exiting the measurement cell. Refer to the MSDS of the chemical in question for
instructions on proper disposal.
3. Sample Point Selection:
There are at least two general concepts to consider when selecting the sample point location. First,
is to select a point that allows reliable determination of the parameter to be measured at the most
critical point for the particular installation. Second, is to take into consideration any chemical injection
control timing. A balance between these considerations must be reached.
Each system is unique, however in general the goal of the chemical injection is to achieve some result
by maintaining a certain measurement at a particular point in the system. For example, to maintain
a specifi c chlorine residual at the exit of the drinking water facility. The location should be selected
so that the injected chemical is already fully mixed so that an accurate sample can be sent to the
measurement cell.
WARNING! Do not run the instrument without sample water running through it. Lack
of, or interruption of water fl ow can cause premature failure of the electrodes.
4
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FIGURE 1 (Sample Water Piping Examples)
It should also be considered that the sample point should be located such that the residual reading
can be used as a control signal for the chemical injection. Especially, it should be considered that if
there is a long time delay between chemical injection changes and the change being detected by the
measurement cell, then chemical injection control is adversely aff ected. The delay time should be
kept as short as possible. We recommend that the time be less than 5 minutes.
5
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FIGURE 2 (Sample Point Sources)
FIGURE 3 (Installation Example)
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4. Mounting the Electrodes: If applicable, install the necessary hardware to mount the electrode. This
may be a separate acrylic pot or a PVC gland that threads into the fl ow cell.
1. Remove the electrode from its buff er cap and place it into its mounting gland. Secure it into place
by gently threading it into the gland, rotating clockwise until it stop.
2. Connect the quick-disconnect cap & cable assembly to the top of the pH or ORP electrode by
gently threading the cap on, rotating clockwise until it stops.
5. Wiring the Electrodes: The WQM-100 will have its electrode connections pre-wired and only the
electrode(s) need to be connected. If an electrode is being added that the unit was not originally
supplied with or if the cable assembly is being replaced, please referece the following installation
points.
NOTE: If installing an electrode that the equipment was not supplied with, it may be necessary to
add an additional liquid tight cable grip into the controller enclosure. This hardware will have been
provided with the new electrode that is to be installed.
1. With the instrument powered off , run the cable portion of the electrodes quick-disconnect cap &
cable assembly through the liquid tight cable grip in the controllers enclosure.
2. Refer the circuit board fi gure (FIgure 8) for wiring connection terminals for the electrode that is
being connected.
6. Installation Inspection: Reference the troubleshooting table in this document if needed.
• Make sure that the sensing glass is fully submerged.
• Make sure that the sensing glass is free of air bubbles.
• There should be a reading on the instrument display.
FIGURE 4 (Mounting Gland, Quick-Disconnect Cap & Cable)
WARNING! Electrical hazards are involved with this installation. Only qualifi ed personnel
should perform this installation.
7
III. CALIBRATION AND PROGRAMMING
1. Conditioning: Before calibration is carried out, the water quality monitor must be operated for
several hours to allow the readings to stabilize.
a. Start the sample water fl ow to the measurement cell(s).
c. An ideal fl ow rate of 500 ml/minute (8 GPH) should be provided. Under all circumstances, the
electrodes must be kept wet, even if the sample water fl ow stops periodically. Maximum sample
water pressure is 5 psig. See Figure 1.
d. Turn on the power to the monitor.
e. Check for air bubbles in the sample line and measurement cell(s). Remove any air bubbles.
f. Allow the equipment to operate with the sample water fl owing for several hours. After this, the
electrode(s) can be calibrated.
2. Programming the WQM-100 Water Quality Monitor
a. Operation (See Section VII): This is the normal operation state of the WQM-100. It provides
a display of the current readings; Temperature, (optional) pH, (optional) ORP, (optional)
Conductivity, Live Charts and any alarm conditions that may exist.
b. Configuration and Calibration (Programming) (See Section VIII): These screens are used to
set up the display options, operational parameters and other features.
c. PID Control (See Section IX): These parameters confi gure the PID Control program in the
software. These parameters perform proportional, set-point or compound loop control. One or
more of the analog outputs (AO1 through AO4) can be programmed to transmit a 4-20 mA control
signal.
3. Programming Access
a. Operation Mode: This is the standard operatonal state during initial powering of the device. To
return to this mode from any other screen simply press the button repeatedly.
b. Configuration and Calibration: This is accessed from the Operation screen by pressing the
button until the password screen is reached. Then enter the password “100” and then press the
button.
c. PID Control: These parameters will display several general status and control screens in the
Operation Mode. Access to the screens which allow this program to be set-up are listed among
the other operational parameters in the Confi guration menus. Press the button (in the
Operation Mode) until the password screen is reached. Then enter the password “100” and press
the button.
4. Operating the keypad
1. Navigation: To move from one screen to another, simply press the and buttons to reach
the desired screen. Navigation between screens is possible in either direction.
2. Adjustment of Displayed Parameters: To adjust a displayed parameter in the Confi guration
Mode, simply use the and buttons to increase or decrease. Once a parameter has been
set to the desired position, pressing either or button to leave the screen will cause the new
parameter to be stored. To select a blinking option (such as “Temperature Cal – Yes/No”), use the
arrow buttons as needed to make the desired selection blink then press the button.
8
FIGURE 5 (Operation Menu Flow Chart)
Enter Password
Begin I/O Hold?
Hold Time
Alarm Status
pH
ORP
Cond
Temp
ORP 620 mV
Temp 70F
(1 hr)
Ph 7.54
(1 hr)
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Cond 0.62 mS
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FIGURE 6 (Hidden Configuration & Live Data Screens)
Cond Live Data
Temp
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IV. EXPLANATION OF OPERATION MODE SCREENS
Main Screen: This screen will display the live readings for installed and active electrodes (e.g. pH, ORP
and/or conductivity) and temperature sensors. The values shown in extra-large font size are live readings. A
value may show in red color if there is an active Alarm condition for the respective electrode.
pH Chart: This screen shows curves which graphically depict pH values for active pH sensors over a user-
adjustable time period. The pH chart will not be present if neither channel 1 nor channel 2 is set for pH.
ORP Chart: This screen shows curves which graphically depict ORP values for active ORP electrode over
a user-adjustable time period. The ORP chart will not be present if neither channel 1 nor channel 2 is set for
ORP.
Conductivity Chart: This screen shows curves which graphically depict conductivity values for active
conductivity electrodes over a user-adjustable time period. The Conductivity chart will not be present if no
conductivity electrodes are present.
Temperature Chart: This screen shows curves which graphically depict temperature values for active
thermistors over a user-adjustable time period.
Alarm Status Screen: This screen will show a list of current alarm conditions for active probes and sensors.
Typically, a non-normal alarm condition will be shown in red color.
Access Screen: In addition to allowing access to the WQM-100 Confi guration screen (after adjusting the
password value to “100”), users can initiate an “I/O Hold” from this screen.
11
FIGURE 7A(Configuration Menus)
pH Setup
Live pH
Live mV
Low Alarm
High Alarm
Cal Mode
Cal 4.0?
Cal 7.0?
pH Setup
Live pH
Live mV
Mode
Low Alarm
High Alarm
Cal Mode
Sample pH
Sample Cal
Fixed pH
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Dead Band
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Lag Time Mode
Lag Time
Flow Variable K
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Flow Setup
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Low Alarm
Threshold
Flow Stop
Flow Min CLC
Filter Time
PO1 Setup
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Control Mode
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When ‘Run Mode’ is set to “Manual” the ‘Manual’ setting
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Configuration 1 of 2
PID Control
Flow Input
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pH Probe
ORP Probe
Cond Probe
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High Alarm
Begin ORP Cal?
ORP Probe Setup
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High Alarm
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When performing a ‘ORP Cal’ the “Live” reading at the top
of the screen becomes adjustable.
12
FIGURE 7B (Configuration Menus)
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13
V. EXPLANATION OF CONFIGURATION MODE SCREENS
WQM-100 Configuration Screen: This screen lists titles of accessible Setup screens for the electrodes,
outputs, data logging, and charting. Use the button to select an option, and then press the button to
access the associated screen(s).
pH Electrode Setup: This screen will show the live readings (in pH and mV) from the pH electrode and
allows the user to change the following values and parameters:
Low Alarm: Adjust the low pH alarm trip-point (in pH).
High Alarm: Adjust the high pH alarm trip-point (in pH).
Cal Mode (pH Calibration Mode): The water quality monitor allows the user to select from four diff erent
pH calibration methods including: ( ‘Sample’, ‘4.0 and 7.0’, ‘4.0 and 10.0’, ‘7.0 and 10.0’ ). The
calibration type to use is completely up to the user. However Hydro Instruments recommends using the
following selection criteria:
A. If pH buff ers are not available, then use the “Sample” calibration. This is only a one point calibration
(your sample) and will automatically calculate an ideal calibration slope. This provides reasonable
accuracy if the sample pH is close to seven and pH of the process is relatively stable.
B. If sample pH is less than seven, use the ‘4.0 and 7.0’ calibration method.
C. If sample pH is greater than seven, use the ‘7.0 and 10.0’ calibration method.
D. If sample stream is subject to wide swings in pH, use the ‘4.0 and 10.0’ calibration method.
Quick notes to increase calibration accuracy:
• Before placing the pH electrode into a buff er for calibration, blot the bottom of the probe with a clean
microfi ber cloth.
CAUTION: Take care not to scratch the probe surface as this will damage the probe and aff ect your
readings.
• Allow the pH meter to sit in the buff er solution for a few seconds prior to calibration. The longer it sits
in the buff er solution, the closer it will be to the ideal value. Generally 15-30 seconds for a new probe.
When calibrating the pH electrode the controller software will count down from 25 seconds to ensure
good calibration.
• Keep the pH sensor and buff er solution still when calibrating your instrument. Vigorous movement of
the sensor can disrupt readings and lead to inaccurate calibrations, should the pH electrodes reading
be disrupted during calibration the countdown will reset.
• Select a pH range for calibration that will be similar to your operating conditions. For example, if the
operating range is 7.80 to 8.10 then perform a 7.00 and 10.00 calibration.
• When calibrating your sensor, always use a fresh buff er solution and discard the buff er after use.
• Be aware of the temperature of the buff ers being used. Generally buff er manufactures write on their
label at what temperature the pH is its true value (generally 77°F, 25°C). Temperature can infl uence
dissociation and thus if your calibration is done with a buff er not at its prescribed temperature, your
calibration will be inaccurate. It is best to calibrate with buff ers that have an accurate pH close to your
operating conditions.
• Air bubbles and other liquids can form around the outside of the sensor and aff ect the accuracy of the
reading. Be sure to remove any air bubbles upon installation.
‘4.0 and 7.0’, ‘7.0 and 10.0’, and ‘4.0 and 10.0’ pH calibration methods:
Cal 7.0? (or Cal 4.0?): Calibrate the lower pH for the selected method and span, following notes below.
Cal 10.0? (or Cal 7.0?): Calibrate the upper pH for the selected method and span, following notes
below.
14
These are two point calibrations carried out with two known pH buff er solutions.
1. In the Temperature calibration screen, set the Temperature mode to manual and enter the actual
buff er solution temperature.
NOTE: pH buffer calibrations are somewhat temperature dependent. pH buffers are usually accurate
at 25ºC. Error in pH readings can occur if buffer temperatures are drastically different from their
prescribed temperature (+/- 5ºC). If the temperature difference is greater than this margin, consider
adjusting buffer temperature or performing a sample calibration.
2. Once the calibration method is selected, the fi rst buff er solution required will be displayed on the
screen. Place the pH electrode into the appropriate buff er and select ‘Begin’.
3. The software waits for the reading to stabilize for 25 seconds before accepting or rejecting it as a
valid calibration point. The countdown timer will appear on the screen in real-time. Note: The pH
value will not be displayed.
4. If the calibration point is accepted, an “accepted” screen will appear. Press down to clear the screen
and the next buff er solution required will appear.
5. Place the pH electrode in the appropriate buff er solution and select ‘Begin’.
6. The software will wait for a stable reading over 25 seconds. If the second calibration point is
accepted, an “accepted” screen will appear. Press down to clear and the pH calibration is complete.
7. Place the pH electrode back into the sample solution and change the Temperature back to the original
operating conditions.
Sample Calibration: This calibration is carried out with the pH electrode left installed in its holding cell
with the sample water fl owing through it. However, be sure that the Temperature displayed on your unit
is accurate before calibrating the pH.
1. If this calibration option has been selected, the following screen will require the operator to enter the
pH of the sample water in which the calibration will be done.
2. Use a hand held pH meter to measure the pH of the sample water and then enter the pH of the
sample on the screen.
3. Before proceeding check that no air bubbles have formed on the tip of the pH electrode. Select
‘Begin’; the software will wait for a stable reading over 25 seconds before accepting or rejecting the
calibration point. If the calibration point is accepted, press the down key and the pH calibration is
complete.
NOTE: If at any point your pH calibration is rejected, the entire calibration procedure will need to be
repeated. If the problem persists, see the troubleshooting section below.
ORP Electrode Setup: This screen shows the live ORP readings (in mV) from its respective ORP electrode
and allows the user to change the following values and parameters:
Low Alarm: Adjust the low ORP alarm trip-point (in mV).
High Alarm: Adjust the high ORP alarm trip-point (in mV).
Single Pt Cal (Single Point Calibration): Press the key to begin ORP calibration.
Conductivity Electrode Setup: This screen shows the live Conductivity readings (in mS/cm) from its
respective conductivity electrode and allows the user to change the following values and parameters:
Low Alarm: Adjust the low conductivity alarm trip-point (in mS/cm).
High Alarm: Adjust the high conductivity alarm trip-point (in mS/cm).
Single Pt Cal (Single Point Calibration): Press the key to begin conductivity calibration.
Temp Sensor Setup: This screen shows the live reading from its respective temperature sensor (thermistor)
and allows the user to change the following values and parameters:
Units: Select ‘F’ (Fahrenheit) or ‘C’ (Celsius)
15
Mode: Select ‘AUTO’ (Automatic) or ‘MANL’ (Manual)
Automatic enables the temperature to be automatically detected via the thermistor.
Manual Temp: This will show ‘OFF’ unless the mode is ‘MANL’, in which case the value is adjustable.
Sample Calibration: This line is visible when the temperature mode is set to ‘AUTO’. The temperature
displayed represents what the program interprets the current temperature reading to be. If necessary,
adjust the displayed temperature using the and buttons.
Alarm and Relay Setup: This screen allows the user to change the following values and parameters for the
four alarm relays (Relay 1, Relay 2, Relay 3, Relay 4):
Alm Mode (Alarm Mode): Select ‘Latching’ or ‘Non-latching’
A latching relay will require manual acknowledgement of any alarm condition (by pressing the [MINUS]
button with the Main Screen active). When Non-Latching is selected, alarms will clear themselves
whenever the alarm condition no longer exists.
Alm Delay (Alarm Delay): Adjust the delay time. Any alarm condition must then exist for this period of
time before tripping the relay. This delay can help avoid false alarms and is recommended to be set at 5
seconds or longer.
Relay 1, 2, 3 or 4: The monitor is equipped with four alarm relays. Each of these relays can be
individually set to represent any of the following alarm conditions:
pH High/Low Alm (pH High or Low Alarm)
ORP High/Low Alm (ORP High or Low Alarm)
Cond High/Low Alm (Conductivity High or Low Alarm)
PV1 Low (PID control water flow low alarm.)
Any Alm (Any of the listed alarm conditions.)
4/20mA Outputs Setup: This screen accesses the settings for the four 4-20mA output channels.
AO1, AO2, AO3 or AO4: Each analog output channel can be individually set to represent one of the
following live readings (with corresponding values shown for 4mA and 20mA outputs):
4mA 20mA
pH (pH) 0 pH 14 pH
Temp (Temperature) 0º C (32º F) 50º C (122º F)
ORP (ORP) ORP Chart Min ORP Chart Max
Cond (Conductivity) Cond Chart Min Cond Chart Max
PO1 (PID Process Output) zero process feed full scale process feed
[HIDDEN] 4/20mA Calibration: This hidden screen can be accessed by holding the button when the
AO3 line is selected (on the 4/20mA Outputs Setup screen). While using an ammeter to measure the output
current, the following calibration values can be adjusted using the and buttons:
NOTE: Adjustable values on this screen are Digital-to-Analog Converter (DAC) values.
AO1 4mA Cal: Adjust the DAC value that corresponds to 4mA for Analog Output 1 (AO1)
20mA Cal: Adjust the DAC value that corresponds to 20mA for Analog Output 1 (AO1)
AO2 4mA Cal: Adjust the DAC value that corresponds to 4mA for Analog Output 2 (AO2)
20mA Cal: Adjust the DAC value that corresponds to 20mA for Analog Output 2 (AO2)
AO3 4mA Cal: Adjust the DAC value that corresponds to 4mA for Analog Output 3 (AO3)
20mA Cal: Adjust the DAC value that corresponds to 20mA for Analog Output 3 (AO3)
AO4 4mA Cal: Adjust the DAC value that corresponds to 4mA for Analog Output 4 (AO4)
20mA Cal: Adjust the DAC value that corresponds to 20mA for Analog Output 4 (AO4)
16
Data Log Setup: This screen allows user to change the following values and parameters for setting the
optional data logger:
Data Log: Select ‘ON’ or ‘OFF’ to enable/disable data logging.
Interval: Adjust the frequency at which data will be recorded.
Set Date: Set the current date (Day, Month, Year). Hidden if Data Log is ‘OFF’.
Set Time: Set the current time (Hour:Minute). Hidden if Data Log is ‘OFF’.
Live Chart Setup: This screen allows the user to change the following values:
Chart Time: Adjust the duration of time shown graphically on the three charts after the Main Screen.
Temp Chart Max: Adjust the maximum temperature shown on the Temperature Chart.
Temp Chart Min: Adjust the minimum temperature shown on the Temperature Chart.
pH Chart Max: Adjust the maximum pH value shown on the pH Chart.
pH Chart Min: Adjust the minimum pH value shown on the pH Chart.
ORP Chart Max: Adjust the maximum ORP value shown on the pH Chart.
For any analog outputs (i.e. AO1 through AO4) set to represent ORP, a 20mA signal will represent this
ORP Chart Max value.
ORP Chart Min: Adjust the minimum ORP value shown on the pH Chart.
For any analog outputs (i.e. AO1 through AO4) set to represent ORP, a 4mA signal will represent this
ORP Chart Min value.
Cond Chart Max: Adjust the maximum conductivity value shown on the Conductivity Chart.
For any analog outputs (i.e. AO1 through AO4) set to represent conductivity, a 20mA signal will represent
the Conductivty Chart Max value.
Cond Chart Min: Adjust the minimum conductivity value shown on the Conductivity Chart.
For any analog outputs (i.e. AO1 through AO4) set to represent conductivity, a 4mA signal will represent
the Conductivity Chart Min value.
17
VI. EXPLANATION OF PID CONTROL SCREENS
PID Control: The PID Control program can be accessed via Confi guration screen 1. It uses the fi rst three
menu options: “PID Contorl”, “Flow Input” and “PO1 Output”. The Confi guration sceens can accessed from
the operation mode, scroll down and enter “100” as the password when prompted.
Control Mode: Select desired control type.
OFF: When “OFF” is selected, the PID Control program will be deactivated.
Flow Pacing: This control type will provide a process output (PO1) proportional to the AI1
proportional input signal (and multiplied by the Dosage setting). This control method does not factor
the eletrode readings in any way.
Set Point: This control type will provide a process output (PO1) that is adjusted as needed to
maintain the “Set Point” value.
Compound (Compound Loop): This control type will provide a process output (PO1) that is adjusted
as needed to maintain the “Set Point” value and also factors in changes registered through the
proportional input signal (and multiplied by the Dosage setting). This control method type will not
appear as an option unless the needed input signals are detected.
Channel: Select the channel (i.e. measurement) that the PID control will use in its calculations (e.g. pH,
ORP or Conductivity).
Set Point: Set the target measurement value that the PID control will use to adjust chemical feed.
Dead Band: This is a dead band around the Set Point. As long as the reading is within (+ or -) this
amount from Set Point, the program will consider the Set Point met. This is used to avoid excessive,
continual adjustments.
Integral: A factor used in the calculation of needed adjustments to the process output. This value ranges
from 0 – 100%. Essentially, the program makes a calculation of how much the output needs to be
adjusted in order to reach Set Point and this factor. Increasing the Integral will increase the rate of each
individual adjustment (and vice versa).
Lag Time: This is the time that elapses between a change in chemical feed rate and the change in
measurement observed by the monitor. The PID Control program will wait-out this amount of time
between each adjustment to PO1. Instruments should be installed to minimize lag time in order to
optimize control (ideally limit this time to less than 5 minutes).
Max Lag Time: A maximum Lag Time, which can be used in Compound Loop Control only. When in
use, this sets limits the maximum lag time that can be calculated by the variable lag time formula.
Lag Time Mode: Select “Fixed” or “Variable”. If “Fixed” is selected, only the “Lag Time” will be used.
If “Variable” is selected, the lag time used will vary as the fl ow varies, but will be limited to the Max Lag
Time.
Flow Variable K: Enter desired fl ow level. If “Variable” is selected, the lag time will be calculated as
follows: Flow at Variable Lag divided by the current fl ow rate and then multiplied by the Lag Time.
NOTE: In applications where flows vary greatly, lag times may also change significantly. In these
instances, the use of variable lag times will improve control timing.
NOTE: If “Fixed” is selected as “Lag Time Method”, the settings of “Max Lag Time” and “Flow at Variable
K” are ignored.
18
Flow Input: This branch accesses the settings for the proportional (fl ow) input.
Dosage (Gain): This value will adjust the ratio of chemical feed to the PV1 water fl ow. It is eff ectively a
multiplication factor that is applied to the calculated chemical feed rate.
Units: Select desired units (MGD, GPM, GPD, LPM, MLD, %, M3/H).
Dec Posn: Select desired decimal position.
Full Scale: Enter the proportional input full scale. This setting should be what a 20 mA proportional
input (AI1) signal represents.
Low Alarm: Enter low fl ow alarm trip point (if desired).
Threshold: This setting allows the user to set a value (above zero) to be treated as zero for the
proportional input (AI1) signal. In proportional (Flow Pacing) control, this would mean the output signal
(PO1) would remain at zero (4mA) until the proportional input reached this value.
Flow Stop: This setting is only used in Compound Loop Control (CDC) to prevent PO1 adjustment
based on the Set Point when PV1 water fl ow has stopped. The user can enter a PV1 water fl ow value
below which the PO1 output will go to and remain at 4mA until the PV1 water fl ow returns to a value
greater than the entered Flow Stop value.
Filter Time: This is an adjustable span of time over which the PV1 input signal will be continually
averaged. It is recommended that it be set to 5-10 seconds.
PO1 Output: This branch accesses the settings for the PID Control output signal.
Units: Select desired units (PPD, GR/H, KG/H, GPH, GPM, GPD, %).
Dec Posn: Select desired decimal place.
Full Scale: Enter the desired output full scale. This is what a 20 mA output signal (selected as PO1) will
represent.
NOTE: A minimum of three integers must be used. Therefore, if the PO1 Full Scale is set below 100,
one decimal position must be used (ex: 99.9)
Control Mode: Select either “Normal” or “Inverted”. These two selections are basic classifi cations of
what chemical type the PID Control program is controlling. “Normal” represents any chemical that will
increase the reading and “Inverted” represents and chemical that will decrease the reading.
Run Mode: The PID control can be set to run automatically “Auto” or the user can input a desired PO1
output value “Manual”.
19
VII. MAINTENANCE AND CLEANING
The quality of the water greatly eff ects the frequency of cleaning that is required. Cleaning requirements
will be diff erent at each installation. Visually checking the condition of the electrodes regularly is the best
way to determine the required frequency of cleaning.
1. Inlet Filter Screen: Some installations may require an inlet fi lter screen to fi lter large particles out of
the sample water. If there is an inlet fi lter screen installed, regularly check the inlet fi lter screen and
condition. If it is found to be dirty, then clean it with clean water before reinstalling.
2. Flushing the Measurement Cell: If water will not fl ow through the measurement cell and their is a
visable blockage then follow this procedure to fl ush it:
a. Turn off the power to the monitor.
b. Remove the fl ush plug in the fl ow cell and allow to drain.
c. Reinstall the fl ush plug.
d. Repeat as necessary before turning the power back on.
3. Thermistor: If the thermistor fails, then it will give a very high or very low signal. To test the
thermistor, follow this procedure:
a. Turn off power to the monitor.
b. Open the monitors NEMA 4x enclosure and remove the two thermistor wires from the MB128
board (RS1 and AIC).
c. Use an ohm meter to check the resistance of the thermistor. If the ohm meter shows a stable
resistance reading around 10 kohms, then the thermistor is not defective. If the reading is zero or
infi nite, the thermistor is defective and must be replaced.
d. After replacement, thermistor recalibration may be required.
e. If the thermistor fails, the monitors temperature mode can be set to “Manual” to allow for proper
operation until a replacement thermistor is installed.
4. pH Electrode: The pH electrode will periodically require replacement. The frequency of replacement
is dependent on the quality of the water. Also, all handling instructions must be followed carefully to
avoid damaging the pH probe. Failure of the pH probe can be indicated by an excessively high or low
reading. If the probe cannot be recalibrated, then it must be replaced. Instructions for replacement
will be included with the replacement pH probes available from Hydro Instruments.
Refer to sections I.1, II.4, VI, and Troubleshooting of this manual.
5. ORP Electrode: The ORP electrode will periodically require replacement. The frequency of
replacement is dependent on the quality of the water. Also, all handling instructions must be followed
carefully to avoid damaging the ORP electrode. Failure of the ORP electrode can be indicated by
an excessively high or low reading. If the probe cannot be recalibrated, then it must be replaced.
Instructions for replacement will be included with the replacement ORP electrode available from
Hydro Instruments.
Refer to sections I.1, II.4, VI, and Troubleshooting of this manual.
6. Conductivity Electrode: The conductivity electrode will periodically require replacement. The
frequency of replacement is dependent on the quality of the water. Also, all handling instructions
must be followed carefully to avoid damaging the conductivity electrode. Failure of the conductivity
electrode will be indicated by an excessively high or low reading. If the probe cannot be recalibrated,
then it must be replaced. Instructions for replacement will be included with the replacement
conductivity electrode available from Hydro Instruments.
Refer to sections I.1, II.4, VI, and Troubleshooting of this manual.
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