Hach Doc023.98.80076 Phd Sc Analog Differential Ph/orp Sensors User Manual

DOC023.98.80076
pHD sc Analog Differential pH/ORP
Sensors
11/2021, Edition 4
User Manual

Section 1 Specifications

Specifications are subject to change without notice.
Table 1 Sensor specifications

Section 2 General information

In no event will the manufacturer be liable for direct, indirect, special, incidental, or consequential damages resulting from any defect or omission in this manual. The manufacturer reserves the right to make changes in this manual and the products it describes at any time, without notice or obligation. Revised editions are found on the manufacturer’s website.

Safety information

The manufacturer is not responsible for any damages due to misapplication or misuse of this product including, without limitation, direct, incidental, and consequential damages, and disclaims such damages to the full extent permitted under applicable law. The user is solely responsible to identify critical application risks and install appropriate mechanisms to protect processes during a possible equipment malfunction.
Please read this entire manual before unpacking, setting up or operating this equipment. Pay attention to all danger and caution statements. Failure to do so could result in serious injury to the operator or damage to the equipment.
Make sure that the protection provided by this equipment is not impaired. Do not use or install this equipment in any manner other than that specified in this manual.

Use of hazard information

  DANGER
Indicates a potentially or imminently hazardous situation which, if not avoided, will result in death or serious injury.

WARNING
Indicates a potentially or imminently hazardous situation which, if not avoided, could result in death or serious injury.

CAUTION
Indicates a potentially hazardous situation that may result in minor or moderate injury.

NOTICE
Indicates a situation that, if not avoided, may cause damage to the instrument. Information that requires special emphasis.

Precautionary labels

Read all labels and tags attached to the instrument. Personal injury or damage to the instrument could occur if not observed. A symbol on the instrument is referenced in the manual with a precautionary statement.

	This is the safety alert symbol. Obey all safety messages that follow this symbol to avoid potential injury. If on the instrument, refer to the instruction manual for operation or safety information.
	This symbol indicates that a risk of electrical shock and/or electrocution exists.
	This symbol indicates the presence of devices sensitive to Electro-static Discharge (ESD) and indicates that care must be taken to prevent damage to the equipment.
	Electrical equipment marked with this symbol may not be disposed of in European domestic or public disposal systems. Return old or end-of-life equipment to the manufacturer for disposal at no charge to the user.

Product overview

This sensor is designed to work with a controller for data collection and operation. Multiple controllers can be used with this sensor. This document assumes sensor installation and uses with an sc200 controller. To use the sensor with other controllers, refer to the user manual for the controller that is used.
The sensor is available in different styles. Refer to Figure 1.

Section 3 Installation

Mounting

Personal injury hazard. Removal of a sensor from a pressurized vessel can be dangerous. Installation and removal of these sensors should be done by individuals trained in proper high pressure and temperature installation. Always use industry-approved hardware and safety procedures when dealing with high pressure and/or temperature fluid transport systems.

WARNING

Personal injury hazard. Removal of a sensor from a pressurized vessel can be dangerous. Installation and removal of these sensors should be done by individuals trained in proper high pressure and temperature installation. Always use industry-approved hardware and safety procedures when dealing with high pressure and/or temperature fluid transport systems.

For examples of sensors in different applications, refer to Figure 2 and Figure 3. The sensor must be calibrated before use. Refer to Calibrate the sensor on page 12.

Connect the sensor to the module

WARNING 
Potential Electrocution Hazard. Always disconnect power to the instrument when making electrical connections.
WARNING 
Electrocution Hazard. High voltage wiring for the controller is conducted behind the high voltage barrier in the controller enclosure. The barrier must remain in place except when installing modules, or when a qualified installation technician is wiring for power, relays or analog and network cards.

NOTICE
Potential Instrument Damage. Delicate internal electronic components can be damaged by static electricity, resulting in degraded performance or eventual failure.
To install the module and connect the sensor, refer to the illustrated steps on page 9 and Table 2.
Note: If the sensor cable is not long enough to reach the controller, an interconnect cable and junction box are required to extend the distance.
Table 2 pH and ORP differential sensor wiring

Section 4 Operation

Guidelines for operation

CAUTION
Personal injury hazard. The glass bulb or shank on the sensor can break. Handle the sensor carefully to prevent injury.

• Remove the protective cap before the sensor is put into the process.
• When the sensor is removed from the process for >1 hour, fill the protective cap with pH 4 buffer (recommended) or tap water and put the cap on the sensor. Repeat every 2–4 weeks for extended storage.

User navigation

Refer to the controller documentation for keypad description and navigation information.
Push the RIGHT arrow key on the controller multiple times to show more information on the home screen and to show a graphical display.

Configure the sensor

Use the Configure menu to enter identification information for the sensor and to change options for data handling and storage. The following procedure can be used to configure pH or ORP sensors.

1. Push the MENU key and select Sensor Setup, [Select Sensor], Configure.
2. Use the arrow keys to select an option and push ENTER. To enter numbers, characters or punctuation, push and hold the UP or DOWN arrow keys. Push the RIGHT arrow key to advance to the next space.

Calibrate the sensor

4.4.1 About sensor calibration
Calibration adjusts the sensor reading to match the value of one or more reference solutions. The sensor characteristics slowly shift over time and cause the sensor to lose accuracy. The sensor must be calibrated regularly to maintain accuracy. The calibration frequency varies with the application and is best determined by experience.
A temperature element is used to provide pH readings that are automatically adjusted to 25 °C for temperature changes that affect the active and reference electrode. This adjustment can be manually set by the customer if the process temperature is constant.
During calibration, data is not sent to the datalog. Thus, the datalog can have areas where the data is intermittent.

4.4.2 pH calibration procedure
Sensors can be calibrated with 1 or 2 reference solutions (1-point or 2point calibration). Standard buffers are automatically recognized. Make sure that the correct buffer set is used (refer to Change calibration options on page 15).

1. Put the sensor in the first reference solution. Make sure that the sensor portion of the probe is fully immersed in the liquid (Figure 4).
2. Wait for the sensor and solution temperature to equalize. This can take 30 minutes or more if the temperature difference between the process and the reference solution is significant.
3. Push the MENU key and select Sensor Setup, [Select Sensor], Calibrate.
4. Select the type of calibration:
   

   Option	Description
   2 point buffer	Use 2 buffers for calibration, for example, pH 7 and pH 4 (recommended method). The buffers must be from the buffer set that is specified in the Cal Options menu (refer to Change calibration options on page 15).
   1 point buffer	Use 1 buffer for calibration, for example, pH 7. The buffer must be from the buffer set that is specified in the Cal Options menu.
   2 point sample	Use 2 samples or buffers of known pH value for calibration. Determine the pH value of samples with a different instrument.
   1 point sample	Use 1 sample or buffer for calibration. Determine the pH value of samples with a different instrument.

5. If the passcode is enabled in the security menu for the controller, enter the passcode.
6. Select the option for the output signal during calibration:
   

   Option	Description
   Active	The instrument sends the current measured output value during the calibration procedure.
   Hold	The sensor output value is held at the current measured value during the calibration procedure.
   Transfer	A preset output value is sent during calibration. Refer to the controller user manual to change the preset value.

7. With the sensor in the first reference solution, push ENTER.
   The measured value is shown.
8. Wait for the value to stabilize and push ENTER.
   Note: The screen may advance to the next step automatically.
9. If the reference solution is a sample, measure the pH value with a secondary verification instrument. Use the arrow keys to enter the measured value and push ENTER.
   Note: If a pH buffer not listed in the Cal Options menu is used, refer to the buffer bottle to find the pH value that corresponds to the temperature of the buffer.
10. For a 2-point calibration, measure the second reference solution (or sample):
    a. Remove the sensor from the first solution and rinse with clean water.
    b. Put the sensor in the next reference solution and push ENTER.
    c. Wait for the value to stabilize. Push ENTER.
    Note: The screen may advance to the next step automatically.
    d. If the reference solution is a sample, measure the pH value with a secondary verification instrument. Use the arrow keys to enter the measured value and push ENTER.
11. Review the calibration result:
    • Passed—the sensor is calibrated and ready to measure samples.
    The slope and/or offset values are shown.
    • Failed—the calibration slope or offset is outside of acceptable limits.
    Repeat the calibration with fresh reference solutions. Refer to Maintenance on page 16 and Troubleshooting on page 17 for
    more information.
12.  If the calibration passed, push ENTER to continue.
13. If the option for operator ID is set to Yes in the Calibration Options menu, enter an operator ID. Refer to Change calibration options on page 15.
14. On the New Sensor screen, select whether the sensor is new:
15. Return the sensor to the process and push ENTER.
    

    Option	Description
    EDIT NAME	The sensor was not calibrated previously with this controller. The days of operation and previous calibration curves for the sensor are reset.
    SENSOR S/N	The sensor was calibrated previously with this controller.

    The output signal returns to the active state and the measured sample value is shown on the measuring screen.
    Note: If the output mode is set to hold or transfer, select the delay time when the outputs return to the active state.

4.4.3 ORP calibration procedure
Sensors can be calibrated with an ORP reference solution or with the process sample.

1. Put the sensor in the reference solution. Make sure that the sensor portion of the probe is fully immersed in the solution (Figure 5).
2. Push the MENU key and select Sensor Setup, [Select Sensor], Calibrate.
3. Push ENTER to select 1 Point Sample calibration.
4. If the passcode is enabled in the security menu for the controller, enter the passcode.
5. Select the option for the output signal during calibration:
   

   Option	Description
   Active	The instrument sends the current measured output value during the calibration procedure.
   Hold	The sensor output value is held at the current measured value during the calibration procedure.
   Transfer	A preset output value is sent during calibration. Refer to the controller user manual to change the preset value.

6. With the sensor in the reference solution or sample, push ENTER.
   The measured value is shown.
7. Wait for the value to stabilize and push ENTER.
   Note: The screen may advance to the next step automatically.
8. If the process sample is used for calibration, measure the ORP value with a secondary verification instrument. Use the arrow keys to enter the value and push ENTER.
9. Review the calibration result:
   • Passed—the sensor is calibrated and ready to measure samples.
   The slope and/or offset values are shown.
   • Failed—the calibration slope or offset is outside of accepted limits.
   Repeat the calibration with fresh reference solutions. Refer to Maintenance on page 16 and Troubleshooting on page 17 for more information.
10. If the calibration passed, push ENTER to continue.
11. If the option for operator ID is set to Yes in the Calibration Options menu, enter an operator ID. Refer to Change calibration options on page 15.
12. On the New Sensor screen, select whether the sensor is new:
    

    Option	Description
    Yes	The sensor was not calibrated previously with this controller. The days of operation and previous calibration curves for the sensor are reset.
    No	The sensor was calibrated previously with this controller.

13.  Return the sensor to the process and push ENTER.
    The output signal returns to the active state and the measured sample value is shown on the measuring screen.
    Note: If the output mode is set to hold or transfer, select the delay time when the outputs return to the active state.

4.4.4 Temperature calibration
The instrument is calibrated at the factory for accurate temperature measurement. The temperature can be calibrated to increase accuracy.

1. Put the sensor in a container of water that is at a known temperature.
   Measure the temperature of the water with an accurate thermometer or independent instrument.
2. Push the MENU key and select Sensor Setup, [Select Sensor], Calibrate.
3. Select 1 PT Temp Cal and push ENTER.
4. Wait for the value to stabilize and push ENTER.
5. Enter the exact value and push ENTER.
6. Return the sensor to the process and push ENTER.

4.4.5 Exit calibration procedure
If the BACK key is pushed during calibration, the user can exit the calibration.

1. Push the BACK key during a calibration. Three options are shown:
   

   Option	Description
   QUIT CAL	Stop the calibration. A new calibration must start from the beginning.
   BACK TO CAL	Return to the calibration.
   LEAVE CAL	Exit the calibration temporarily. Access to other menus is allowed. Calibration for a second sensor (if present) can be started. To return to the calibration, push the MENU key and select Sensor Setup, [Select Sensor].

2. Use the arrow keys to select one of the options and push ENTER.

4.4.6 Change calibration options
The user can set a reminder or include an operator ID with calibration data from the CAL OPTIONS menu.

1. Push the MENU key and select Sensor Setup, [Select Sensor], Calibrate, Cal Options.
   

   Option	Description
   SELECT BUFFER	For pH sensors only—changes the set of buffer solutions that are recognized for calibration to pH 4.00, 7.00, 10.00 (default set) or DIN 19267 (pH 1.09, 4.65, 6.79, 9.23, 12.75) Note: Other buffers can be used if the 1 point sample or 2 point sample option is selected during calibration.
   CAL REMINDER	Sets a reminder for the next calibration in days, months or years—Off (default), 1 day, 7, 30, 60, or 90 days, 6 or 9 months, 1 or 2 years
   OP ID on CAL	Includes an operator ID with calibration data— Yes or No (default). The ID is entered during the calibration.

2.  Use the arrow keys to select an option and push ENTER.

4.4.7 Reset calibration options
The calibration options can be reset to the factory default options.

1. Push the MENU key and select Sensor Setup, [Select Sensor], Calibrate, Reset Default Cal.
2. If the passcode is enabled in the security menu for the controller, enter the passcode.
3. Push ENTER. The Reset Cal? the screen is shown.
4. Push ENTER. All calibration options are set to the default values.
5. If the option for operator ID is set to Yes in the Calibration Options menu, enter an operator ID. Refer to Change calibration options on page 15.
6. On the New Sensor screen, select whether the sensor is new:
   

   Option	Description
   Yes	The sensor was not calibrated previously with this controller. The days of operation and previous calibration curves for the sensor are reset.
   No	The sensor was calibrated previously with this controller.

7. Push the BACK key to return to the measuring screen.

Impedance measurements

To increase the reliability of the pH measurement system, the controller determines the impedance of the glass electrodes. This measurement is taken every minute. During diagnostics, the pH measurement reading will be on hold for five seconds. If an error message appears, refer to the Error list on page 19 for more details.
To enable/disable the sensor impedance measurement:

1. Push the MENU key and select Sensor Setup.
2. Select Diag/test and push ENTER.
3. Select Imped Status and push ENTER.
4. Select Enable/Disable and push ENTER.

To see both actual and reference sensor impedance readings:

1. Push the MENU key and select Sensor Setup.
2. Select Diag/test and push ENTER.
3. Select sensor signals and push ENTER.

Modbus registers

A list of Modbus registers is available for network communication. Refer to the manufacturer’s website for more information.

Section 5 Maintenance

WARNING
Personal injury hazard. Only qualified personnel should conduct the tasks described in this section of the manual.

Maintenance schedule

The maintenance schedule shows minimum times for regular maintenance tasks. Perform maintenance tasks more frequently for applications that cause electrode fouling.

Clean the sensor

WARNING 

Chemical exposure hazard. Obey laboratory safety procedures and wear all of the personal protective equipment appropriate to the chemicals that are handled. Refer to the current safety data sheets (MSDS/SDS) for safety protocols.

WARNING 
Personal injury hazard. Removal of a sensor from a pressurized vessel can be dangerous. Installation and removal of these sensors should be done by individuals trained in proper high pressure and temperature installation. Always use industry-approved hardware and safety procedures when dealing with high pressure and/or temperature fluid transport systems.

Pre-requisite: Prepare a mild soap solution with a non-abrasive dishwashing detergent that does not contain lanolin. Lanolin leaves a film on the electrode surface that can degrade the sensor performance. Examine the sensor periodically for debris and deposits. Clean the sensor when there is a buildup of deposits or when performance has degraded.

1. Use a clean, soft cloth to remove loose debris from the end of the sensor. Rinse the sensor with clean, warm water.
2. Soak the sensor for 2 to 3 minutes in the soap solution.
3. Use a soft bristle brush to scrub the entire measuring end of the sensor.
4. If debris remains, soak the measuring end of the sensor in a dilute acid solution such as < 5% HCl for a maximum of 5 minutes.
5. Rinse the sensor with water and then return to the soap solution for 2 to 3 minutes.
6. Rinse the sensor with clean water.

Note: Sensors with antimony electrodes for HF applications may require additional cleaning. Contact technical support.
Always calibrate the sensor after maintenance procedures are done.

Replace the salt bridge

Differential sensors have a removable salt bridge (Figure 6). If the sensor has been cleaned but fails calibration, replace the salt bridge and the standard cell solution. Refer to the instructions included with the salt bridge.

1. Salt bridge
2. Differential sensor

Always calibrate the sensor after maintenance procedures.

Section 6 Troubleshooting

Intermittent data

During calibration, data is not sent to the datalog. Thus, the datalog can have areas where the data is intermittent.

Test the pH sensor

Pre-requisites: Two pH buffers and a multimeter.
If calibration fails, first complete the maintenance procedures in Maintenance on page 16.

1. Put the sensor in a pH 7 buffer solution and wait for the temperature of the sensor and buffer to reach room temperature.
2. Disconnect the red, green, yellow and black sensor wires from the module.
3. Measure the resistance between the yellow and black wires to verify the operation of the temperature element. The resistance should be between 250 and 350 ohms at approximately 25 ºC.
   If the temperature element is good, reconnect the yellow and black wires to the module.
4. Measure the DC mV with the multimeter (+) lead connected to the red wire and the (–) lead connected to the green wire. The reading should be between –50 and + 50 mV.
   If the reading is outside of these limits, clean the sensor and change the salt bridge and standard cell solution.
5. With the multimeter still connected the same way, rinse the sensor with water and put it in a pH 4 or pH 10 buffer solution. Wait for the temperature of the sensor and buffer to reach room temperature.
6.  Compare the mV reading in the pH 4 or 10 buffer to the reading in the pH 7 buffer. The reading should differ by approximately 160 mV. If the difference is less than 160 mV, call technical support.

Test the ORP sensor

Pre-requisites: 200 mV ORP reference solution, multimeter.
If calibration fails, first complete the maintenance procedures in Maintenance on page 16.

1. Put the sensor in a 200 mV reference solution and wait for the temperature of the sensor and solution to reach room temperature.
2. Disconnect the red, green, yellow, and black sensor wires from the module.
3. Measure the resistance between the yellow and black wires to verify the operation of the temperature element. The resistance should be between 250 and 350 ohms at approximately 25 ºC.
   If the temperature element is good, reconnect the yellow and black wires to the module.
4. Measure the DC mV with the multimeter (+) lead connected to the red wire and the (–) lead connected to the green wire. The reading should be between 160 and 240 mV.
   If the reading is outside of these limits, call technical support.

Sensor diagnostic and test menu

The sensor diagnostic and test menu show current and historical information about the instrument. Refer to Table 3. To access the sensor diagnostic and test menu, push the MENU key and select Sensor Setup, [Select Sensor], DIAG/TEST.

Table 3 Sensor DIAG/TEST menu

Error list

When an error occurs, the reading on the measurement screen flashes and all outputs are held when specified in the controller menu. To show the sensor errors, press the MENU key and select Sensor Diag, [Select Sensor], Error List. A list of possible errors is shown in Table 4.
Table 4 Error list for pH and ORP sensors

Warning list for sensors

A warning does not affect the operation of menus, relays and outputs. A warning icon flashes and a message is shown on the bottom of the measurement screen. To show the sensor warnings, press the MENU key and select Sensor Diag, [Select Sensor], Warning List. A list of possible warnings is shown in Table 5.
Table 5 Warning list for pH and ORP analog sensors

Event list for sensors

The event list shows current activities such as configuration changes, alarms, warning conditions, etc. To show the events, press the MENU key and select Sensor Diag, [Select Sensor], Event List. A list of possible events is shown in Table 6. Previous events are recorded in the event log, which can be downloaded from the controller. Refer to the controller documentation for data retrieval options.
Table 6 Event list for pH and ORP sensors

Section 7 Replacement parts and accessories

Note: Product and Article numbers may vary for some selling regions. Contact the appropriate distributor or refer to the company website for contact information.

pHD sensors

LCP and Ryton encapsulated sensors

HACH COMPANY World Headquarters
P.O. Box 389, Loveland, CO 80539-0389 U.S.A.
Tel. (970) 669-3050
(800) 227-4224 (U.S.A. only)
Fax (970) 669-2932
[email protected]
www.hach.com

© Hach Company/Hach Lange GmbH, 2011-2012, 2021. All rights reserved. Printed in Germany.