Liquid Analyzers

The input module you need depends on the Model Number of your FLXA Analyzer.

If you forgot the password to your FLXA Transmitter you can use the password #PW123# - this will allow you go into the menus. Remember to change or remove the password.

Soak the sensor in 5 - 10% Hydrochloric acid (HCl) in water solution. for 5 - 10 minutes, then rinse. If you have trouble finding 5 - 10% HCL you can buy muriatic acid at a building supply house and it is usually 20 - 30% HCL. Check the label. Dilute it with tap water to get something close to 10%. 

BE VERY CAREFUL WHEN DILUTING THE ACID. USE PROTECTIVE CLOTHING (GLOVES, FACE SHIELD ETC.) ALWAYS ADD ACID TO WATER, NEVER ADD WATER TO ACID.

If you forget the password you have set in one of these transmitters there are only 9 passwords that can be set. 

The password setting on the unit is a little difficult to understand. When you put a 3 digit code in service code 52 you are setting up 3 passwords, not just 1. The first digit is for the maintenance mode (calibration) The second digit is for the commissioning mode (when you hit the * key) The third digit is for the service menu (when you hit yes on the SERV menu under commissioning). 

Here are the password options: 

1 = 111
2 = 333
3 = 777
4 = 888
5 = 123
6 = 957
7 = 331
8 = 546
9 = 847 

So, and example:

if you setup a password of 1.2.3:

• To calibrate you would have to enter 111 
• When you hit the * key the password would be 333
• To access the SERV menu the password would be 777

There are no bypass passwords, these are the only passwords available for the unit.

If you have lost the password for your SC150 you can use password   #PW123#   to get into the menu. The next thing you should do is to reset the password.

There is no way to "turn off" an unused input on a DC402. If you leave the terminals open you will get error messages. 

Connect a simulated sensor to the unused input to clear the errors. Use a resistor on 11-12 to simulate the temp sensor, 1000 ohms for PT1000, 100 Ohms for PT100. Simulate the same type temperature sensor that the other channel is using. 

Use a resistance to simulate the cell that gives a conductivity reading within the range, usually 1000 ohms between 14-15 will work. Once you have connected the resistors the input the errors will clear.

The difference is the temperature sensor. The SC41 has a Ni100 temperature element and the SC42 has a PT1000 temperature element. PT1000 is a better temperature element, but some old electronics will not accept a PT1000 temperature element, so the SC41 is still available.

Click the link at the top of the page to download the DO400 Manual.

How to startup a new sensor, or how to replace the Membrane Cap and Electrolyte.

Startup of a new Oxygold G sensor:

The Oxygold G sensor is shipped dry with a protective cap over the end of the Membrane Cartridge.

CAUTION: The electrolyte should not be allowed to touch your skin or clothing. Use Personal Protective Equipment such as gloves and protective eyeware when working with the electrolyte.

1. Inspect the new sensor for damage during shipment. 

2. Remove the membrane cartridge and rinse it once with a small amount of the OXYGOLD G electrolyte. 

3. Using the installed pipette dispense 1.5 ml. of the OXYGOLD G electrolyte into the membrane cartridge.

4. Maintain the membrane cartridge in a vertical position to prevent spilling the electrolyte, and insert the sensor shaft and screw it in place. Rinse off any electrolyte that may remain on the exterior of the sensor. 

5. The sensor must now polarize to remove the oxygen that is dissolved in the electrolyte. This can be accomplished by connecting the sensor to a transmitter and turning on the power. It will take 2 hours for the polarization to be completed. Normally the next step will be to perform an air calibration so you should leave the sensor in air during this polarization period. 

6. Perform an air calibration. 

Replacing the membrane cartridge and electrolyte

1. Remove the membrane cartridge and discard any remaining electrolyte. Do not attempt to polish or even wipe the anode and cathode of the sensor. 

2. If the membrane cartridge is being replaced discard the old cartridge and follow the steps below with the new cartridge. If it is being reused, follow the steps below with the old cartridge. 

3. Rinse the membrane cartridge once with a small amount of the OXYGOLD G electrolyte.

4. Using the installed pipette dispense 1.5 ml. of the OXYGOLD G electrolyte into the membrane cartridge.

5. Maintain the membrane cartridge in a vertical position to prevent spilling the electrolyte, and insert the sensor shaft and screw it in place. Rinse off any electrolyte that may remain on the exterior of the sensor. 

6. The sensor must now polarize to remove the oxygen that is dissolved in the electrolyte. This can be accomplished by connecting the sensor to a transmitter and turning on the power. It will take 2 hours for the polarization to be completed. Normally the next step will be to perform an air calibration so you should leave the sensor in air during this polarization period. 

7. Perform an air calibration. 

We also have a video you can watch of the OxyGold G startup process. Click the link at the top of this page.

You can test the ISC converter by simulating a conductivity reading using an ISC40 sensor.

• You will need:
  • A known working ISC40 sensor.
  • A piece of wire
  • One or two decade box/resistance sources.
• Connect sensor wires 13-17 to analyzer.
• Connect wire through the toroidal sensor and connect the wire to the decade box. Be sure not to cross the leads or wire.
  
• Use second decade box resistance source to simulate the temp sensor.
  • If you don’t have a second resistance source you can just connected the temp sensor wires 11&12 from the sensor, you will just not be able to vary the input readings.
• Write down the Cell Constant, change it to 1.000
• Set the temperature to the reference temperature or: Write down the Temp. Compensation method, and change it to “None.”
• The Conductivity reading should be 1/R where R = Resistance on the decade box.
• If you need higher resistance than the decade box you can use multiple loops of wire through the sensor.  The reading will be L² / R where L = Number of loops, R = Resistance on the decade box.
• Return all settings to the original settings when finished.

• With an Ohm meter check the following wires on the ISC40G sensor cable:
  • 11 to 12 (Pt1000 or Thermistor)
  • 13 to 17 – Sensor coil – expect low resistance. If unstable or above 100Ω it is bad.
  • 15 to 16 - Sensor coil – expect low resistance. If unstable or above 100Ω it is bad.
  • 14 to every other wire – The ohm meter should stay off scale. If the ohm meter moves/jumps/reads anything that is bad.

Simulating a conductivity reading on an ISC convertor.

• You will need:
  • A known working ISC Converter
  • A piece of wire
  • One or two decade box/resistance sources.
• Connect sensor wires 13-17 to analyzer.
• Connect wire through the toroidal sensor and connect the wire to the decade box. Be sure not to cross the leads or wire.
  
• Use second decade box resistance source to simulate the temp sensor.
  • If you don’t have a second resistance source you can just connected the temp sensor wires 11&12 from the sensor, you will just not be able to vary the input readings.
• Write down the Cell Constant, change it to 1.000
• Set the temperature to the reference temperature or: Write down the Temp. Compensation method, and change it to “None.”
• The Conductivity reading should be 1/R where R = Resistance on the decade box.
• If you need higher resistance than the decade box you can use multiple loops of wire through the sensor.  The reading will be L² / R where L = Number of loops, R = Resistance on the decade box.
• Return all settings to the original settings when finished.

Use the link at the top of the page to download a compressed (ZIP) file containing the GS Sheet and Manual for the SC150.

The TM20 pH meter was discontinued over 20 years ago, but the manual is still available. 

If you have trouble downloading it, send us an email at support@us.yokogawa.com or call 800-524-7378.

To test the conductivity input do the following: 

1. Write down the cell constant and change it to 1.00 (this is not mandatory, it makes the math easier) 
2. Place a jumper wire between 13 to 14 and another one on 15 to 16 (not necessary on the DC400/402) 
3. Place a resistance between the 13/14 and 15/16 connection. If the unit is set in resistivity it should match the resistance. If it is displaying conductivity it should read Y where Y = (cell constant)/(input resistance) and the units are Siemens. So if the result is 0.005 Siemens this equals 5 milliSiemens.and 0.000005 Siemens equals 5 microSiemens. 

Remember to set the cell constant back to the original value if you changed it.

A tiny crack in the membrane of a glass electrode is not always visible to the naked eye. Frequent shocks may create cracks in the glass that cause measurment errors. These cracks will cause the analyzer to read 0 mV and the analyzer interprets that to a reading near pH 7. in many process the setpoint is near pH 7. This means a cracked pH sensor can cause an inaccurate reading that is near the setpoint, and it may not be noticed quickly. This can be a critical and dangerous situation.   Without additional diagnostic, the error will not be detected until the process is out of control.

Yokogawa's Transmitters have an impedeance check function. The analyzer checks the impedance of pH (and reference) sensors via the solution ground. The Transmitter can be set to generate an alarm if the impedance limits are exceeded. 

It is very important that the cables maintain a very high impedance. If any moisture penetrates the cable the impedance will drop and the cable will short out the voltage generated by the pH sensors. This will cause errors or a total loss of measurement.  This can also occur if the cables are exposed to water for long periods of time. To insure that the pH measurement remains accurate protect the cables and the back of the pH sensors from exposure to moisture. 

Yes. The Cation Differential pH and ORP sensors have a glass electrode that needs a 2 point calibration performed regularly. Because of the Cation Reverence electrode you must use special buffers with a constant sodium ion concentration. This calibration is needed to compensate for the change in response of the glass electrodes. These changes are normal and are caused by aging or chemical attack, and they are accelerated at higher temperatures. 

Error 130 & 131 are display errors. The PH450 calibrates the display each time it powers up. Error 130 or 131 means this calibration failed. Cycle the power to the unit and allow it to calibrate the display again. If after 6 times the error is still present, the unit will need to be returned to our Repair Center. Call 800-524-7378 and ask for the repair center, then ask for a Return Authorization number, or email us at support@us.yokogawa.com and ask for a Return Authorization number. Include the following information, Company name, billing and shipping addresses, a Contact name, phone number and email address, the complete model number and serial number, and a description of the problem.

The PH150 and SC150 were discontinued in 2004. The Manual and General Specification sheet are no longer available on Yokogawa's website. Use this link to download a zip file containing both documents.

Often, Instrumentation technicians like to shorten cables to match the installation. This is strongly discouraged with Analytical Sensors. Yokogawa has designed cables with a special layer of conductive plastic to ensure maximum noise immunity. This layer can be very difficult to remove. If done improperly the shortened cables will often give intermittent problems. They may show noisy signals, signals that jump when the cables are touched or moved, or may not work at all. This is often difficult to diagnose and may lead to customers replacing the entire system because they lose confidence in the integrity of the analyzer. For this reason we recommend that the cables be left at their original length. Any unused cable can be coiled up and immobilized using Plastic Wire-ties or tape to keep it out of the way and prevent wind or weather from causing it to move.

Keep in mind that pH analyzers are measuring a voltage signal through the glass of the pH sensor. This sensor may have over 1,000 MegOhms of resistance. In these conditions the cables must be perfect to keep the voltage signal from leaking away before it reaches the Transmitter. Even the oil from your fingers in the wrong place can short out this signal and cause errors. 

The PH150 allows the use of passwords to limit access to the Calibration functions and access to the Configuration functions. If these functions have been protected with a password and the password is not available there is a way to bypass the protection and change or remove the passwords.

Use the following as the password:  #PW123#   

This will allow you to access the Configuration menu. Go immediately to the Advanced Setup menu and then to the Passwords menu.

You can enter a blank password, or enter a new password that you can remember. Once this is done you can proceed to your other tasks.

Yokogawa's pH and conductivity sensors include a temperature sensor to allow for temperature compensation. The pH and conductivity sensors have a relatively large temperature mass and respond slowly to the changes in the process temperature. This is fine for temperature compensation or diagnostic uses but not for process control of the temperature. Process temperature sensors have a much lower mass and respond much quicker to temperature changes. Use those for process control, not the temperature sensor built into the pH or Conductivity sensor. 

That is possible but not guaranteed. The 225 mm sensor body is longer, so it has more electrolyte. Often the reference electrode fails because the electrolyte is depleted as it diffuses through the reference junction into the process. With a higher volume of electrolye this process will take a longer time. This is not the only failure mode so you can still have a short lifetime due to another cause.

In a dual input FLXA202 or FLXA21 analyzer you can use a HART Splitter to convert the HART® dynamic variables into current outputs or contact outputs. The model number is "1W-KFD2-HLC-EX1.D" and the description is "P+F HART Splitter." In the FLXA menu you can select which dynamic variables you like as "SV" "TV" and "FV."

Go to Commissioning>Advanced Setup>Communication>HART> then use the down arrow to select the SV, TV, and FV fields.

Generally we state that the pH analyzer is as accurate as the care that is given to the device allows.

• With lots of care you can achieve 0.05 pH accuracy.
• With normal care you achieve 0.1 pH
• Without care the measuring error can be pH 0.5 or more.

The official specifications from the GS Sheet are shown below:

Most pH sensors with a glass membrane cannot be mounted upside down. To absorb the thermal expansion of the internal buffer solution there is always a sizeable air bubble inside the sensor. When the sensor is mounted upside down the reference element can lose contact with the electrolyte. The FU24 pH sensor from Yokogawa can be used in upside down application, because it has a special design that allows us to reduce the size of the air bubble. The PH18 sensor can be mounted upside down because it does not have a glass electrode or electrolyte.  

Yokogawa offers the PH18 sensor. This sensor is nonglass and suitable for regular CIP and SIP cycles.

Yes you can, but we do not recommend this method. A pH sensor has a reference electrode that has a low impedance to the process. If the process suffers from common mode voltages or ground loops it will be difficult to measure the pH accurately. These cause current to flow through the path of least resistance. If there is no better choice this will be the reference electrode. This results in measurment errors. (Ohm’s law: 1 uA through 10 kΩ is 10 mV is 0.2 pH) and can result in damage to the reference electrode.

With a solution ground the path of least resistance becomes the solution ground and the pH sensor does not suffer from ground loop currents.

Also the famous Yokogawa impedance monitoring features work properly only when we have a solution ground. If you want to connect a sensor without a solution ground, then you can connect a jumper from the reference input terminal to the liquid earth input terminal. On Yokogawa Transmitters this is usually terminals 13 and 14. 

Cleaning pH Sensors

Basic Steps 

• Rinse electrode in clean water
• Clean by immersing the electrodes in a cleaning solution (see below). 
• Rinse Again
• Check with buffers

Cleaning Solutions:

If you know a specific way to clean the sensors for your process use that method. Often Hot Water is sufficient. In many cases 5 - 10% Hydrochloric acid (HCl) in water will work for stubborn deposits. If you have trouble finding 5 - 10% HCL you can buy muriatic acid at a building supply house and it is usually 20 - 35% HCL. Check the label. Dilute it with tap water to get something close to 10%. 

BE VERY CAREFUL WHEN DILUTING THE ACID. USE PROTECTIVE CLOTHING (GLOVES, FACE SHIELD ETC.) ALWAYS ADD ACID TO WATER, NEVER ADD WATER TO ACID (this can cause the water to boil and splash acid out of the container).

Cleaning Process:

First, rinse off the electrodes/sensor in just plain water. To remove any heavy process coating use a soft brush, taking care not to damage the electrodes. Greasy or sticky deposits may respond to a mild detergent, but limit the time the sensor is exposed to keep the detergent from penetrating the reference junction. Rinse well after using detergent.

Most process deposits will be removed if you immerse the electrodes in an acid cleaning solution for 5 - 10 minutes, agitating them regularly. Use a soft brush to clean off any remaining coating deposits. If the coating is extreme this could take longer.

Now rinse the electrodes thoroughly again with clean water to remove any detergent or acid that would contaminate the buffer solution used.

Dry and place the electrodes in a new clean pH buffer solution and allow it to stabilize. If the displayed value is within ±0.03 pH of the buffer value, the electrodes are clean and do not require calibration. Put the system back on line. If the value is outside the tolerance (± 0.03 pH), then a two point buffer calibration is required.

If you have set a password and have forgotten it you can use the password "MOON" to get into the configuration menu. Then you will be able to modify/view the password that is set in the unit. 

Note: if you have not set a password just hit enter on the screen and it will accept that as the password.

The password to get in all the maintenance and commissioning menus is 16 

The short answer to this question is NO.

But, there is a long answer that will give you another option.

Yokogawa has created a Submersible Sensor Kit (part number M1289XT) for the FU20 pH sensors - M1289XU for the FU24 sensor). It is also known as the “Dangler.” 

It consists of a short enclosed section with threads that fit the threads on the back of the FU20/24 sensor. The enclosed section is large enough to contain the strain relief on the standard FU20/24 or the connector on the Variopen version. There is a compression fitting that the cable passes through that is designed to make a watertight seal with the cable. Once installed in the Dangler you CAN simply drop the FU20/24 into your tank or open channel.

This is the Japanese GS sheet, containing a number of options we rarely sell here in the US. Contact Support at 800-524-7378 or support@us.yokogawa.com for price and delivery information. 

NO! 

Sensors that are not used need to be stored in a solution that guarantees that the sensor is ready for use. When the sensor is stored in pure water the salt will be washed out of the junction of the reference cell. This causes the sensor to fail. 

Yokogawa uses the same salt concentration in the wet pocket (during shipment and storage) as is used inside the sensor. For combination sensors we add a trace of acid to keep the Glass membranes active. So, the best method is to keep the wet pocket that was shipped with the sensor and store the sensor in the wet pocket when not in use.

Most of our pH sensors have a noble metal solution ground and our transmitters measures two values: 1.  the voltage between this solution ground, or liquid earth sensor and the pH sensor, and 2. the voltage between this solution ground, or liquid earth sensor and  the reference cell. This allows the transmitter to use this voltage to calculate the ORP value. The beauty of this solution is that with one combination pH/ORP sensor and one Transmitter you can get both pH and ORP values. 

This is a well-known pH problem that we call Diffusion Potential. If the sensor junction is partially plugged the electrical contact between electrolyte and process is not good. This results in a high diffusion potential and an error in the measurement. The chemical composition of the pH buffers is different from the process solution. So when the junction is partially plugged it creates a diffusion potential that adds to the potential from the pH buffers, and you calibrate for this total potential. When you return the senors to the process the diffusion potential changes causing a shift in the pH value displayed by the Transmitter.

An easy check is to look at the diagnostic information on the pH analyser: Is the Asymmetry Potential high or the Slope low? If either occurs then most likely you have this problem. You can try cleaning the sensor to reduce the diffusion potential.

Another cause can be the infamous ground loop current. This can occur when you use pH sensors without a liquid earth connection.

Yes and No. 

Yes - after cleaning you need to verify that the analyzer is reading correctly. The easiest way is to see how it reads when placed in 2 pH buffer soltuions. This is what you do when calibrating. 

No - If the readings are within the specifications (+/- 0.01pH, +/- 1 mV for ORP) in the pH buffers a full calibration is not needed. 

Another way to verify that the readings are correct is to take a process sample and accurately determing the pH or ORP value using another method. This may be a Handheld or Portable analyzer, or you may take a sample to the lab. Be aware that there are many processes that will read differently after the sample sits in a sample bottle for a period of time. For those samples the lab reading will be different from the On-line analyzer. 

Yes, the SENCOM Module in these sensors allows a Modbus Master to
connect using Modbus RTU protocol and access the following data:

• pH
• Temperature compensated pH
• ORP
• pH compensated ORP
• rH
• Temperature
• Junction resistance value
• Sensor details (Model, Serial Number, production date)
• Sensor calibration data (zero, slope, temperature offset)
• Sensor status signals (e.g. Glass impedance detection)

As shown in the diagram above, our pH is calculated by subtracting value B from value A. To do this the B value is stored inside the sensor and can be displayed independently at any time. Since ORP is simply the value of B, we can easily display both pH (A-B) and ORP (B) without any issues.

Yes, the input module can be changed in the Converter. 

See the FAQ:

Which Input Module do I order for my FLXA21/202 analyzer?