At CENSAR Technologies, Inc, we've done our best to create a Web site  that anticipates and satisfies our customers' needs. With that goal in mind,  we've compiled a list of frequently asked questions. If you do not find an  answer to your question here, contact us at  info@censar.com or  (941) 894-6575.

Q - What is  the minimum flow requirement?
A - The minimum flow requirement for the  Six-CENSE sensor is 2 cm/s (compared to 10-30 cm/s required by conventional  membrane sensors).

Q - How can I tell if my location is experiencing low flow?
A - There are a few indications that the Six-CENSE instrument  is in a low flow environment. Things to watch for are:
(1) an increase in DO  accompanied by a decrease in pH while the other parameters stay in range,
(2) a drift negative of the counter voltage outside of the standard  operating range (- 300 mV) for extended periods of time,This is associated with poor hydration not low flow, unless there is data to the contrary
(3) a  drift in pH that exceeds 0.5 pH units over the course of two weeks.

Q- How often do I need to calibrate the unit?
A- The  Six-CENSE unit should only need to be calibrated monthly. In situations where  there is large variation in pH and/or Chlorine levels (1.5-2 pH units, 2 mg/L in  chlorine), calibrations may be needed more frequently.

Q - Can I  calibrate all of the parameters at once?
A- It is recommended that  parameters be calibrated individually. The suggested order of calibration is as  follows: Temperature, Conductivity, pH, Chlorine, and Dissolved Oxygen (or  Monochloramine). Calibration of REDOX is not recommended. Before making a second calibration change, it is recommended that you allow sufficient time for the  preceding parameter to display a stable output.

Q- What is ORP, How  does ORP relate to chlorine?
A- ORP is a measure of the oxidation  potential of the most powerful REDOX pair in the solution. In the case of  chlorinated water, this also depends on pH and temperature, but has a general  level that is determined by the presence of chlorine. ORP does not indicate  concentration. In chlorinated water, expect a value between 650-750mV. In  monochloraminated water, expect a range around 450-650mV. As soon as the last  chlorine molecule disappears, the REDOX will drop. An iron pipe, with corrosion

Q - What happens if I scratch the chip?
A- Buy a new one.-Scratching or otherwise touching the surface of the chip should always be avoided. The surface of the chip has very fine, gold microlines. Oils from your  fingers, particulate debris and/or scratching can cause damage to the microlines  and as a result, the chip will not function properly. CTI recommends the use of  a vacuum pen when handling the chips and care should always be taken not to  touch the chip surface.

Q - What happens if the chip is powered and  it dries out?
A - BEFORE the Six-CENSE is removed from a distribution  site, the unit should be powered down and AFTER extraction from the pipe the  chip should be rinsed with deionized water. If the chip is removed from the flow of water and the power is left supplied to it, any impurities or particulates in  the water will be bakedĚ onto the chip. Generally, in these instances, the chip  will be permanently damaged and a new one will have to be installed. If the  damage is not extensive, it is sometimes possible to wash the chip in a dilute  acid solution to remove the foreign material and return it to service.

Q- What happens if the chip loses power and is left wet?
A - Without power, the Six-CENSE anti-fouling mechanism is rendered inoperable. In  chlorinated, flowing water this should not be a problem for short periods of  time. In stagnant, chlorine-free water there will be a build-up of material on  the chip and it will need re-cleaning/hydration before use again. As time passes  without power supplied to the unit, particles suspended in the water will adhere  to the surface of the chip. Particles stocking to the chip are caused by dirty  water, low/no flow and not being installed at an angle (thus allowing bits to  settle out). In an unpowered state, minerals and ionic components of water, as  well as algae and other organics, are free to settle on and otherwise foul the  chip. If this happens, the chip can generally might be recovered by washing it  in a dilute acid solution. Define dilute acid solution.

Q - What  happens if the chip is left in water but without flow?
A -A chip that  remains powered in water without flow will not show accurate readings until the  flow is returned to normal. As part of the chip’s measurement procedure, it  produces electrons to create an acidic environment. When no flow is present to  remove the localized area of acidity, the chip will report low pH values, a  decrease in dissolved oxygen, and low values of chlorine. As the flow is  returned to normal, the chip will once again respond correctly to changes in  water quality.Any other permanent effects will depend on the hardness of the  water in extreme conditions the counter will become coated with limescale.

Q -How do I clean the chip?
A -In general say you don’t. IF  the unit is installed properly and run without moving it, chip cleaning will not  be necessary. If it is, use 1 MHCl, no stronger, and then for a few seconds, or  when it stops fizzing. Generally, if the chip can be cleaned, it will occur  quickly. Also, RINSE the chip BEFORE you put the acid on. Should the chip need  to be cleaned, it should be done so in a dilute acid solution. Do not leave the  chip in the acid solution for prolonged periods (<1 min, if that) of time as  it may cause damage to the microlines. Upon completion of the cleaning process,  rinse the chip with deionized water. DO NOT mechanically dry the surface of the  chip! To dry the chip, let the water evaporate or carefully apply air across the  surface of the chip (as from the coolest and lowest setting on a hair dryer).

Q - When do I need to change the chip/reference electrode?
A-  CTI quotes a chip and reference electrode life of six months under normal  drinking water conditions. Many of our customers have found that they are able  to get useful data from chips that have been in service for longer periods. The  key to determining the life and quality of measurement from the chip/reference  electrode is to keep a close eye on the counter voltage readings. As the  reference electrode gets depleted, the value will drift in the negative  direction. In general, you will know that it is time to replace the reference  electrode when the value is -0.6V or lower. pH drift is also an accurate  indicator of impending reference electrode doom.

Q - Is this system  safe to use in our drinking water supply?
A- Yes! The Six-CENSE unit is  an NSF approved instrument and is completely safe to use in public drinking  water.

Q - Can the unit be installed near a pump, valve or bend in  the pipe?
A- The optimal installation site is in a straight section of  pipe without any pumps or frequently used valves in the immediate area. The  water turbulence associated with pumps, valves and bends in the pipe can lead to  a noisy signal from the sensor. This assertion that we cannot cope with  turbulent water might only be relevant if there is gas in the line which is  being turned into lots of very small bubbles. In our lab flow rig, we measure  just fine at high flow rates, very turbulent water. The bigger problem is  electrical noise associated with being close to pumps.

Q - How do I¬ know if the unit is responding to changes in water quality?
A - If the  unit is installed in a location with sufficient flow and has been calibrated  properly, any changes or variation you see in the six parameters should be  indicative of a change in water quality. To check the accuracy of the  instrument, you can always measure a sample on-site with your reference  instrument(s).

Q - If one parameter on the chip goes bad, do I lose  the other parameters on the chip?
A - In general, no, but in some  instances you may see a change in the other parameters. The chlorine and  dissolved oxygen portion of the chip use the conductivity and pH values as a  reference in their calculations. NOT Currently true, although the facility  exists in the software. Because of this relationship, if either Conductivity or  pH readings were to go “bad,Ě you would observe a similar change in the chlorine  and dissolved oxygen readings. If the chlorine, dissolved oxygen, or redox  portions of the chip were harmed, you would only see problems with the  corresponding channel and no other parameters. You should find that the  parameters are independent of pH and conductivity over all normal ranges  experienced in tap water, but please check this on a good unit.

Q -  How far into the pipe must the chip be inserted?
A - In general, the  deeper the probe is inserted into the pipe, the more contact it will have with  the flow of water and as a result, the happier it will be. Eh? The chip is  either in the flow, or it isn’t. If it is occasionally out of water because of  air in the pipe ,this is another matter. While there is no maximum insertion  depth, CTI recommends specifies a minimum insertion depth of 1 inch (25mm) into  the flow to ensure accurate measurement.

Q - Why do I need to  recalibrate the chip, shouldn’t the cleaning cycle maintain its health?
A - Because the chip is in a constant flow environment and takes a reading every two minutes, the surface is gradually worn down or abraded. As the chip  wears, the measurements will drift due to the change in electrochemistry caused¬ by the abrasion. A monthly calibration corrects for these changes in the chip  surface.

Q - Do I need to remove the unit from the pipe each time I  calibrate? How often do I need to remove the unit from the pipe?
A- No.  System calibrations are done while the instrument is in the water flow and  therefore needs to remain inside of the pipe. Water samples needed for reference  measurement can be drawn from the sample port located on the shaft seal housing.  The only time the unit will need to be removed from the pipe is during the  installation of a new chip and/or reference electrode.

Q - To which  areas of the unit can I apply grease? Is the grease safe for the drinking water?  Why can’t I apply grease to the o-rings that come in contact with the chip?
A - Any grease applied to the unit should be certified for drinking water  applications. CTI recommends Dow Corning 111 Silicone Compound, an NSF approved  material. Grease may be applied to the shaft, the o-rings on the reference  electrode, and to the o-ring on the lower side of the shaft seal housing. Grease  should never be applied to the o-rings that come in contact with the chip.  Grease in this area may reduce the integrity of the watertight seal around the  contact area, which may lead to leaking and a malfunction of the chip. Silicone  Grease on the chip will creep across the measuring surfaces, and stop it from working properly. It will help to seal nicely, though.

Q - How often  and how do you clean the CT-CENSE optics?
A- The cleaning frequency of  the CT-CENSE optics will depend on the aquatic environment in which it is  installed. Waters with a high organic load tend to cause fouling more quickly  than in cleaner water. To clean the CT-CENSE optics, CTI recommends gently wiping  with a cotton swab dipped in <1M HCl or rubbing alcohol and following with a  deionized water rinse. Failing that, a toothbrush in clean water. The optics are  sapphire, thus highly resistant to scratching.

Q - My unit will be  installed in a cold vault, the water won’t freeze, but the electronics might, is that a problem?
A- No. The electronics in the SIX CENSE systems are  rated for temperatures below freezing.

Q - How long does it take to  calibrate the unit?
A - Calibration times may vary, but as a general  rule, the calibration can be performed in 30 minutes. If all of the parameters  require calibration, it may take slightly longer. The time involved is  attributed to taking the reference measurement. and allowing the parameters to stabilize before moving on to the next parameter.

Q - My CT-CENSE  isn’t showing any fluctuation, is something wrong?
A - If you feel your  water is varying in color and/or turbidity and the CT-CENSE is not indicating  such changes, you may need to clean the CT optics. To clean the CT-CENSE optics,  CTI recommends gently wiping with a cotton swab dipped in <1M HCl or rubbing  alcohol and following with a deionized water rinse.

Q - The  CENSETools program shows one reading and my SCADA system shows another value what’s wrong?
A - Most often, this problem is related to the scaling factors.  To check, use a multimeter to be sure that 4-20 mA output readings are in  agreement with the CENSETools values. Also check to see if the calibration cable is plugged into the junction box if applies. If the numbers agree, check the SCADA  system scaling provided in the CENSAR user manuals.

Q - Why do I need to rinse the chip and probe with deionized water when I take it  out of service?
A - When the chip is allowed to dry out, any impurities  that may be in the water can/will be deposited on the surface of the chip. These  deposits may damage the microlines or be difficult to remove at a later date.  Rinsing with deionized water will wash away any impurities and leave a clean  surface when the chip dries.

Q - I logged a file in CENSETools, but I  can’t find it. What do I do?
A - The default directory for all CENSETool  files is C:/Program Files/CENSETool. If your file cannot be found at that  location, use the search feature provided by your computers operating system to  look for the file name. If you start another log file, CENSETools will bring up  a window asking for the new file name. This window will show the directory used  for storing log files.

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Updated 06.12.2009