The AST52, AST41 and AST50 sensors shown to left in standard configuration without waterproofing option installed. Sensors are available for all possible installation types including inline, immersion, submersible, sanitary and HOT-TAP valve retractable schemes.
Shown below is handheld communicator (HHC) automatically detecting that a conductivity sensor has been connected.
Shown to left is AST41 sensor with WPIT sealing and braid-reinforced sealing hose factory installed to make sensor suitable for use in outdoor installations with moisture, rain as well as washdowns.
Alternate waterproofing sealing options are available for fully submersible use even when an immersion rod or standpipe is not used for installation.
CLICK HERE for complete webpage on SMART DIGITAL HiQDT MODBUS RTU MEASUREMENT SYSTEM for core information that is shared for all measurement types and details on the ASTI supplied PLC & HMI packages for turn-ready commissioning. See installation guide for additional details & information.
IMPORTANT NOTE: Smart Digital HiQDT sensors are always RS485 MODBUS RTU slaves. Only ONE of the RS485 MODBUS RTU master devices detailed above can be connected at any one time.
Core Structure of HiQDT RS485 MODBUS RTU Smart Digital Sensors Installed into Field Service
The core difference of the HiQDT smart digital sensors is that all user functionality is accessible via the open standard and royalty free RS-485 MODBUS RTU protocol. This is in contrast to the now antiquated sensors and transmitters that only provide a 0-20mA or 4-20mA current loop or 0-5 or 0-10 VDC voltage output containing no diagnostic information whatsoever. The modern HiQDT smart digital sensors take advantage of the industrial internet of things (IIoT) where remote access to all information is available from the sensor in real-time allowing for advanced predictive maintenance and support including remote calibrations and troubleshooting. HiQDT smart digital sensors create an open and collaborative environment for process automation and liquid analytical monitoring enabling a level of connectivity and integration that is not possible with closed architectures such as HART, Profibus, Fieldbus and other proprietary platforms that force vendor lock-in to the client.
Detailed complete documentation is available for the HiQDT smart digital sensors to allow access to all of the user adjustable configuration parameters, analytic data & calibration functions and values as well as sending the engineered temperature compensated process pH & ORP values in very high resolution. Analytics allow for predictive analytics to schedule maintenance in a proactive manner as well as robust monitoring of the process no matter the control system that is currently employed at the given facility. This HiQDT platform gives customers the freedom to interface these sensors with any PLC of their choice so long as it can act as a RS-485 MODBUS RTU master. Support for RS-485 MODBUS RTU master mode on PLC now is very common, if not altogether standard, even for entry level PLC, many of which are also now available with cost-effective remote ethernet access options.
The major paradigm shift of the HiQDT smart digital MODBUS sensors and the Industrial Internet of Things (IIoT) means that not only process values can be viewed remotely but ALL functionality that is possible locally standing in front of the HiQDT controller can also be accomplished remotely with robust security and administration for access control. That means fewer trips out in the field to assist clients with commissioning or troubleshooting for any issue that is simply a matter of configuring software or setting controller options. All of these types of changes can be made remotely with the HiQDT platform building upon the power of the Industrial Internet of Things (IIoT) and accessibility through wired and wireless networks from a Windows PC as well as cellular connected iOS and Android smartphones and tablets. The ability to send email notifications upon any type of trigger event such as reaching a user defined min or max threshold setpoints for the process or temperature reading as well as fault conditions such as loss of communication with sensor mean excellent field maintenance & support even when site is not open to receiving outside visits due to the pandemic.
The smart digital HiQDT conductivity sensors with integral MODBUS RTU communications allows for simple & fully portable installation scheme. Sensor may be calibrated anywhere (lab, shop or field) and interfaced with any data acquisition or control system in the field via the RS-485 MODBUS RTU communications. The temperature offset and process value offset calibrations can be done with sensor left in service to agree with a reference value from an external measurement device (please see calibration instructions for details). Waterproof & corrosion-resistant NEMA6P rated HiQ4M snap connector are standard for easy seamless hot-swap of sensors from service for cleaning, recalibration and other maintenance tasks as may be required as well as eventual replacement of sensor in time.
Mechanical & Thermal |
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Housing: | Defined by Conductivity Model & Config |
Mounting: | Inline, Immersion, Submersible, HOT-TAP & Sanitary as per sensor installation scheme |
Rating: | Fully submersible and waterproof without use of immersion tube with correct sealing option |
Connector: | NEMA 6P rated HiQ4M male snap connector for HiQDT snap extension cables; Extension cables for 3TX-HiQ platform can also be used for HiQDT type smart digital sensors as well |
Max Cable: | Up to 3,280 feet (1,000 meters) using 22 AWG leads when employing 12VDC power supply |
Temp.: | Inline max per sensor specs; Submersible Use limited to Max 85℃ for all sensor models |
Pressure: | Up to 500 psig inline use for selected models |
Weight: | Varies depending upon sensor type & config |
Dimensions: | Minimum size is ½ ” MNPT for inline installations with AST10/AST51 Sensors; Minimum size is ¾” MNPT for HOT-TAP Valve Retractable Installations; Minimum size is ¾” TRI-CLOVER for |
Electrical |
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Operating VDC: | 8.0 to 13.0 VDC at sensor board |
Power Supply: | Isolated & Regulated 9V or 12V DC |
Current draw: | Max 35mA Absolute, Typical ~30mA |
Conductivity Ranges: | See Tables for Available Range Modes for each Cell Constant |
Temp Sensor: | Integral Platinum 1000Ω TC Element |
Temp Range: | -40 to +210℃ ±0.3℃ (limited by actual sensor specifications) Max Temp is +85℃ at sensor board (submersible) |
Temp. Comp.: | Automatic for all measurements |
Digital Output: | Isolated RS-485 MODBUS RTU |
Baud rate: | 9600 or 19,200 kbps (selectable) |
Compatibility: | ASTI Handheld Communicator (HHC) or Windows HiQDT software or any PLC with isolated RS-485 input that can serve as a MODBUS RTU master to HiQDT sensor slave |
CE mark: | EN61326A |
Range Scaling Factor | 200 | Max Temp. Compensated Conductivity using 2% per ℃ Coefficient | ||||
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Cell Constant (K) | Max Raw Input Limit | Resolution | Lowest Recommended Measurement @ 25℃ | @ 25℃ | @ 75℃ | @ 125℃ |
0.01 | 200 | 0.004 | 2 | 200 | 100 | 66.67 |
0.02 | 400 | 0.008 | 4 | 400 | 200 | 133.33 |
0.05 | 1,000 | 0.02 | 10 | 1,000 | 500 | 333.33 |
0.10 | 2,000 | 0.04 | 20 | 2,000 | 1,000 | 666.67 |
0.20 | 4,000 | 0.08 | 40 | 4,000 | 2,000 | 1,333.33 |
0.50 | 10,000 | 0.2 | 100 | 10,000 | 5,000 | 3,333.33 |
1.00 | 20,000 | 0.4 | 200 | 20,000 | 10,000 | 6,666.67 |
2.00 | 40,000 | 0.8 | 400 | 40,000 | 20,000 | 13,333.33 |
3.00 | 60,000 | 1.2 | 600 | 60,000 | 30,000 | 20,000.00 |
5.00 | 100,000 | 2 | 1,000 | 100,000 | 50,000 | 33,333.33 |
10.00 | 200,000 | 4 | 2,000 | 200,000 | 100,000 | 66,666.67 |
20.00 | 400,000 | 8 | 4,000 | 400,000 | 200,000 | 133,333.33 |
Range Scaling Factor | 200 | Max Temp. Compensated Conductivity using 2% per ℃ Coefficient | ||||
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Cell Constant (K) | Max Raw Input Limit | Resolution | Lowest Recommended Measurement @ 25℃ | @ 25℃ to to 75℃ | @ 125℃ | @ 175℃ |
0.01 | 2,000 | 0.04 | 20 | 1,000 | 666.67 | 500 |
0.02 | 4,000 | 0.08 | 40 | 2,000 | 1,333.33 | 1,000 |
0.05 | 10,000 | 0.2 | 100 | 5,000 | 3,333.33 | 2,500 |
0.10 | 20,000 | 0.4 | 200 | 10,000 | 6,666.67 | 5,000 |
0.2 | 40,000 | 0.8 | 400 | 20,000 | 13,333.33 | 10,000 |
0.5 | 100,000 | 2 | 1,000 | 50,000 | 33,333.33 | 25,000 |
1.00 | 200,000 | 40 | 2,000 | 100,000 | 66,666.67 | 50,000 |
2.00 | 400,000 | 8 | 4,000 | 200,000 | 133,333.33 | 100,000 |
3.00 | 600,000 | 12 | 6000 | 300,000 | 200,000.00 | 150,000 |
5.00 | 1,000,000 | 20 | 10,000 | 500,000 | 333,333.33 | 250,000 |
10.00 | 2,000,000 | 40 | 20,000 | 1,000,000 | 666,666.67 | 500,000 |
20.00 | 4,000,000 | 80 | 40,000 | 2,000,000 | 1,333,333.33 | 1,000,000 |
* Sensor can toggle between standard/high range mode range mode while in use. Standard/high range mode sensor is one configuration and associated sensor board hardware. Ultralow range mode sensor is a different configuration and associated sensor board. While you can toggle between standard and high range modes you cannot toggle between the standard/high and ultralow modes since these are two different sensor boards. Two slope calibrations are stored in dual mode standard/high sensors; slope low is used for the standard mode and slope high for the high mode. Slope calibrations are automatically assigned based upon range mode in use for sensor at time when calibration is performed. The ultralow range mode only uses the single low slope (slope high is unused).
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CELL CONSTANT
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Color Coding | Available in Cell Constant | |
Not available in that Cell Constant |
All sensors are available in smart digital HiQDT MODBUS RTU configuration although not all cell constants are available for each model. Use the standard & high range mode cell constant table above & ultralow range mode table below to determine most suitable selection for your sample. Cell constants above K=2.00/cm omitted from ultralow range table but available on request.
Range Scaling Factor | 2 | Max Temp. Compensated Conductivity using 2% per ℃ Coefficient | ||||
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Cell Constant (K) | Max Raw Input Limit | Resolution | Lowest Recommended Measurement @ 25℃ | @ 25℃ | @ 75℃ | @ 125℃ |
0.01 | 2 | 0.00004 | 0.02 | 2 | 1 | 0.667 |
0.02 | 4 | 0.00008 | 0.04 | 4 | 2 | 1.333 |
0.05 | 10 | 0.0002 | 0.1 | 10 | 5 | 3.333 |
0.10 | 20 | 0.0004 | 0.2 | 20 | 10 | 6.667 |
0.20 | 40 | 0.0008 | 0.4 | 40 | 20 | 13.333 |
0.50 | 100 | 0.002 | 1.0 | 100 | 50 | 33.333 |
1.00 | 200 | 0.004 | 2.0 | 200 | 100 | 66.667 |
2.00 | 400 | 0.008 | 4.0 | 400 | 200 | 133.33 |
Total dissolved solids (TDS) units are computed from measured conductivity. The curves that define relationship between the measured conductivity and user selectable total dissolved solid (TDS) units of NaCl, KCl or 442 are preprogrammed into sensor with full range of 0 to 100,000 ppm. The actual usable range may be limited by the choice of cell constant and range mode in which the sensor is operated.
Other types of total dissolved solids (TDS) for other electrolytes or electrolyte mixtures can be programmed into the sensor on a special-order basis (minimum order requirements apply for such special programming requests). Inquire to the factory if you have need for such special TDS units for your smart digital HiQDT MODBUS RTU conductivity sensors.
Salinity computed from the measured conductivity. Curves that define the relationship between measured conductivity and the computed salinity in PSU are preprogrammed into the sensor with a full range of 0.000 to 50.000 PSU.
The actual supported range may be limited by cell constant & range mode used). Contact the factory to determine the most suitable sensor model and cell constant configuration for your desired salinity range of interest.
The conductivity of pure water varies significantly with temperature in a well-defined but non-linear fashion as detailed in the graph to left. This behavior is preprogrammed into the HiQDT-CON-L MODBUS RTU conductivity sensors for the automatic temperature compensation feature to make it suitable for ultrapure water (UPW) type applications.
Although the recommended cell constant for performing conductivity measurement in UPW is K=0.01/cm for best resolution and lower bounds of measurement there may be situations where this K=0.01/cm cell constant cannot be used for the planned installation location because of limitations such as piping arrangement and low-flow. The higher cell constants of K=0.05/cm or K=0.10/cm can be used instead in such cases albeit they require the sample to be at a higher temperature to ensure best results. Table below details recommended minimum temperature for various cell constants for use in UPW. The minimum temperature for UPW measurement for each cell is determined based upon the lowest absolute conductivity value for which the cell constant is recommended & temperature at which this conductivity occurs for UPW. Resistivity are computed units are the inverse of the measured conductivity value.
Range Scaling Factor | 2 | ||||
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Cell Constant (K) | Raw Max Input @ 25℃ | Resolution | Lowest Recommended Absolute Measurement | Minimum Temp ℃ * | Absolute MegaOhm (MΩ) @ Min Recommended ℃ * |
0.01 | 2 | 0.00004 | 0.02 | 8 | 50 |
0.05 | 10 | 0.0002 | 0.1 | 40 | 10 |
0.10 | 20 | 0.0004 | 0.2 | 55 | 5 |
* Minimum recommended temperature is conductivity of UPW which is 1% of ultralow range mode for the given cell and the associated MegaOhm units. Measurements can be performed below the recommended minimum temperature with an associated higher uncertainty for those situations.
For ultralow range conductivity sensors the 5th read input register (30005) sends the computed resistivity MegaOhm (MΩ) using the user defined linear automatic temperature compensation (ATC) while the 6th read input register (30006) sends computed resistivity MegaOhm (MΩ) using the special non-linear ultrapure water style automatic temperature compensation. The resistivity values sent as 0 to 50,000 steps corresponding to 0.000-50.000 MegaOhm (MΩ) for both the 5th (30005) & 6th (30006) read input registers. Theoretical temperature compensated resistivity value can never go above 18.18 MegaOhm (MΩ) for uncontaminated pure water since this is the ideal value at 25 degrees Celsius.
Temperature compensated conductivity and resistivity are referenced back to the 25 ℃ condition for all ATC. Ultrapure water with no contaminants has a value of 0.055 μS/cm conductivity or 18.18 MΩ in resistivity. The most common units for measurement of pure water is resistivity (MΩ) MegaOhm due to high resolution and convenient scaling in the very low conductivity levels. Temperature compensated conductivity and computed resistivity values sent for the ultralow range mode smart digital HiQDT-CON-UL style MODBUS RTU conductivity sensors as well as the raw conductivity.
Graph above shows relationship between the resistivity of pure water at various temperatures. Computed resistivity MegaOhm (MΩ) units are the inverse of measured conductivity and so are the mirror image of the conductivity at various temperatures for ultrapure water (UPW). Graph above shows absolute raw resistivity at various temperatures. Resistivity values sent include ATC referencing reading to 25 ℃ state.
Range Scaling Factor | 2 | Max Temp. Compensated Conductivity using 2% per ℃ Coefficient | |||||
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Nominal Cell Int ** | ACTUAL Cell Constant | Max Raw Input Limit | Resolution *** | Lowest Recommended Measurement @ 25℃ | @ 25℃ | @ 75℃ | @ 125℃ |
10 | 0.01 | 20 | 0.0004 | 0.2 | 20 | 10 | 6.667 |
20 | 0.02 | 40 | 0.0008 | 0.4 | 40 | 20 | 13.333 |
50 | 0.05 | 100 | 0.002 | 1.0 | 100 | 50 | 33.333 |
100 | 0.1 | 200 | 0.004 | 2.0 | 200 | 100 | 66.667 |
200 | 0.2 | 400 | 0.008 | 4.0 | 400 | 200 | 133.33 |
500 | 0.5 | 1,000 | 0.02 | 10.0 | 1,000 | 500 | 333.333 |
1000 | 1.0 | 2,000 | 0.04 | 20 | 2,000 | 1,000 | 666.67 |
2000 | 2.0 | 4,000 | 0.08 | 40 | 4,000 | 2.000 | 1,333.33 |
* Range mode defined by register 40018. When register 40018 is 2 then range scaling factor is ultralow mode. This register 40018 is read only for the ultralow mode sensor type.
** The nominal cell constant of conductivity sensor is found by dividing integer obtained from register 40019 by 100.
*** The resolution is always 50,000 steps no matter the nominal cell constant of sensor or range mode that is in operation.
If sensor used is only ever just one cell constant and range mode, then simple scaling of 0-50,000 steps to conductivity range is possible. Procedure below supports any cell constant in any range mode without changing programming of MODBUS RTU master PLC device:
It is not possible to tell whether the sensor that you have is the Ultralow style or the Ultralow-10X style simply from looking at register 40018 since this would be 2 in both cases. The only way to tell that you have the Ultralow-10X style hardware is that the nominal cell constant detailed in register 40019 will be 10 times higher than the actual cell constant as indicated on the sensor label. This ten-fold deviation between the nominal and the actual cell constant is what is to be expected if you have purchased the Ultralow-10X style sensor. The range of the Ultralow-10X follows what would be expected if the actual cell constant was ten times higher for the same ultralow sensor configuration. Contact factory if you should have any questions or concerns prior to ordering.
For Installations WITH Compression Fitting
For Installations WITHOUT Compression Fitting
Drawing valid for K= 0.05, 0.10, 0.20, 0.50, 1.0 & 2.0 /cm cells. Position of vent hole & associated insertion depth differs for low cells of K= 0.01 & 0.02 /cm & high cells K= 5.0, 10.0 & 20.0 /cm. Inquire to factory for drawings of these alternate cell constants. Smaller valve retractable configuration employing ¾”MNPT full port ball valve with ½”O.D. sensor available upon request.
For Installations WITH Compression Fittin
For Installations WITHOUT Compression Fitting
For Installations with CPVC Sensor Body
For Installations with 316SS Sensor Body