HiQDT Smart Digital Modbus Measurement System

The HiQDT smart digital sensors have integral industry standard RS-485 MODBUS RTU communications allowing them to be connected directly with a very wide array of devices thus ushering in a new era in industrial field measurement where the brand of data acquisition and control device is altogether decoupled from the manufacturer of the smart digital sensor giving true freedom of choice back to the customer to select their preferred vendors for each aspect of the continuous liquid analytical electrochemical analysis without any artificial restrictions.



The HiQDT product line is designed to allow for seamless integration with either customer supplied PLC & HMI or else available as turn-key plug and play packages from the ASTI factory ready for commissioning right out of the box. Systems are available for continuous inline measurement and control in hazardous or safe locations employing rugged LED or advanced touchscreen interfaces. The same HiQDT smart digital RS485 MODBSU RTU sensor used for continuous measurements can also be employed for intermittent measurements when used with an ultralow power battery or solar datalogger to record measurements and then wirelessly transmit this data from remote site locations. ASTI Windows setup and calibration software for HiQDT smart RTU sensors allows for adjustment of all user accessible parameters as desired and is provided free of charge. The battery-powered handheld communicator provides a very simple method for plug and play calibration and setup of various adjustable parameters in the field or in the workshop. Since all calibration and configuration information is integral to the sensor this allows for plug and play hot-swap use between any mating device that has been properly configured without any special user action required in the field.

Introduction to Novel Smart Digital HiQDT Measurement Platform

The HiQDT product line is an altogether novel approach on how to measure, analyze, control and datalog pH & ORP measured parameters for industrial processes automation, discharge compliance and environmental monitoring applications entering in the Industrial Internet of Things (IIoT) age.


Core Structure of HiQDT RS485 MODBUS RTU Smart Digital Sensors Installed into Field Service

NOTE: HiQDT sensors are RS485 MODBUS RTU slaves. Only ONE of the RS485 MODBUS RTU masters detailed below can be connected at any one moment time. See installation guides for details and additional information.

  • Programmable Logic Controller (PLC)
  • Windows Software for Setup, Configuration & Calibration of HiQDT sensors
    • Required for all installation schemes to assign the sensor node address and baudrate
    • Optional for configuration & calibration if these features are not implemented in HMI+PLC
    • Windows Datalogging & Graphing software to record pH, ORP, temperature and raw mV
      values for setup of modbus network & commissioning plus pilot & research applications
  • Handheld Communicator (HHC)
    • 9V battery powered operation with simple easy to use 4 button operation with bright LED
    • Ready for plug & play use right out of the box with zero configuration required

Industrial Internet of Things (IIoT)

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 realtime 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.


1MF-3EA-HiQ4FP-HiQDT-4EA-SCG-PS12 Triple Input Bridge Box with integral 12VDC power supply to energize sensors for 85 to 265 VAC line powered operation with PNCE 6331-6631-HiQDT-WPC Slurry, Sulfide & Extreme Dehydration Resistant Submersible RS-485 MODBUS RTU Smart pH Sensor with waterproofing style “C” sealing option on left and PN 6353-HiQDT-STUB Immersion Slurry Resistant “STUBBY” style back-end cable assembly shown on the right. All connectors are NEMA 6P rated waterproof with bridge box NEMA 4X rated ready for field installation. White & green leads on left are modbus network in while white & green leads on right are out to modbus network.

Significance of HiQDT Platform in the Field

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 be accomplished remotely with robust security and administration for access control. That means no more trips out in to the field to assist clients with commissioning or troubleshooting for any issue that is simply a matter of configuring software or 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 the accessibility through wired and wireless networks both from a Windows PC as well as cellular connected iOS and Android smartphones and tablets. The ability to send email notifications upon user configurable trigger conditions such as max or min process values and temperatures, max days in service since calibration or relay being energized allows for proactive site support & maintenance.

Installation Schemes DIY to Turn-Key Plug & Play

It is not necessary to be a PLC programmer to use the HiQDT smart digital MODBUS sensors. The HiQDT product platform includes a complete set of tightly integrated mating controllers and process equipment to interface the HiQDT sensors with robust factory support to provide completely turn- key field ready plug and play packages. The packages include integral scalable analog outputs, configurable MODBUS RTU and TCP slave digital communications, programmable contact relays, datalogging and full remote access capabilities for all functionality that is possible locally. Although all functionality can be achieved programming your own PLC, the convenience of factory supplied and supported controllers for smaller projects or fast delivery situations might still be very desirable. Factory supplied HiQDT touchscreen controllers include autobuffer calibration with temperature correction for pH buffers to ensure accurate results no matter the operator at the site. Plug and play packages available for hazardous areas requiring Class I, Division II approval as well as for even the most stringent Class I, Division I explosion-proof rated areas with severe & aggressive environments.

Communicator for HiQDT Smart Digital pH & ORP Sensors

HiQDT-EX-LEDTX explosion-proof controller with PN 6353-HiQDT-STUB Slurry Resistant “STUBBY” RS485 MODBUS RTU smart digital pH sensor. Calibration & configuration with free of charge Windows software (see below) or handheld communicator. See details in specification sheet & installation instructions in complete manual. For non-hazardous safe areas lower cost LED Panel & NEMA 4X controller has the same core features as EX unit.

Lightweight portable 9V battery powered handheld communicator (HHC) calibrates & configures HiQDT smart digital RS485 MODBUS RTU sensors at any location. All values stored in non-volatile sensor EEPROM for hot-swap portability when units are installed back into field service

    • 30 hours of total time in use with Lithium 9V battery (15 hours for alkaline 9V) with automatic shutdown when not in use
    • Replaceable 9V battery also powers connected HiQDT sensor

  • Node scanning feature for ease of finding address on connected sensor
  • The following values are stored in non-volatile EEPROM memory inside the
    sensor board for complete installation portability & hot-swap use:
    • Offset calibration for temperature for pH or ORP sensor
    • Offset calibration for pH or ORP sensor
    • Acidic slope for pH sensor used when reading < pH 7
    • Alkaline slope for pH sensor used when reading > pH 7
    • The max & min °C in service & total time in use (energized) o Serial & Item Number & Build Date stamped for traceability
  • The calibrations values and time since that ‘Cal’ was last performed are displayed using ‘View’ key in the various Cal LED modes
  • Intelligent software on HiQDT communicator auto-detects sensor type connected & loads the appropriate options such that one communicator can interface all possible types of HiQDT smart digital MODBUS sensors
  • Quick disconnect cables to 1,000 meters (3,280 feet); NEMA 6P & IP67 rated waterproof HiQ4M & HiQ4F snap connectors for rugged field use
    • 5 feet (1.5m) cable with HiQ4FP female snap connector for HiQ4M male snap connectors of RS845 MODBUS RTU sensors
  • Input Data Ranges & Max Resolution for pH and ORP Measurements: o pH range of -2 to +16 with 0.001pH resolution
    • ORP range of ±1000 or ±2000mV; 0.1mV resolution
    • Temperature range of -40 to +210 °C; 0.1°C resolution
  • Perform 1-point offset anywhere in the range. Slope calibrations are
    automatically assigned for acidic (-2 to +7) or alkaline (7 to 16) pH ranges yielding a 3-point point overall calibration scheme with a dual slope for optimal accuracy at any pH (can be very important for batch systems)
  • Offset calibrations only for ORP measurement and temperature.
  • Automatic Temperature Compensation (ATC) for pH measurement
    • pH values always automatically include current calibrations
  • Can perform in-situ offset calibrations & spot measurement in the field



Handheld communicator (HHC) has 3-digit display & 16 LEDs to show readings & analytic data as well as to calibrate and configure sensor. Programming is done by 4 key front panel. ‘Mode’ key used to toggle and navigate to each LED. ‘Up’ or ‘Down’ buttons scroll available options & adjust values. ‘Mode’ key is used to make selections and save entries. ‘View’ key provides additional information for the given LED mode (see table for details on use of ‘View’). Once baudrate & node of connected sensor are entered parameters are automatically loaded for zero configuration plug & play use in the field.

HHC with PN 6353-HiQDT-STUB Immersion Slurry Resistant “STUBBY” RS-485 MODBUS RTU Smart Digital HiQDT pH Sensor compact configuration particularly ideal for portable field use.

Factory Supplied Turn-Key Ready Controllers for HiQDT Sensors

Factory supplied controllers for the HiQDT pH & ORP sensors built upon very well established Maple Systems PLC & HMI hardware. Customized hardware & software features are offered if scope of project envisioned justifies the associated NRE & MOQ needed for the special order request.


HiQDT-CTRL-6CH six (6) channel controller with 7.0” color touchscreen is shown above. The three (3) and six (6) channel controllers using the 7.0 inch color touchscreen are available in configurations that are suitable for use in hazardous Class I, Division II locations while the two (2) channel controllers using the smaller 4.3 inch color touchscreen are only suitable for use in safe non-hazardous installation locations.


Features and Options:

  • Assembly Type
    • NEMA 4X rated supplied with all hardware ready for immediate wall or pipe mounting.
  • Power Configurations
    • Isolated 24VDC ± 15% (PS0) | 85-264 VAC (PS1) | Non-Isolated 18-75/9.5-36 VDC (PS2/3)
    • Isolated 12VDC power supply for HiQDT sensors included with all power configurations.
  • Display Type
  • Certifications
    • All HiQDT controllers have CE, CSA & UL approvals for use in non-hazardous areas
    • 6 Channel & 3 Channel units available for use in Class I, Division II hazardous locations
HiQDT-CTRL-2CH dual channel controller with 4.3” touchscreen HMI shown with lid & swivel plate open. Modular design & construction allows for replacement of only the touchscreen HMI if damaged in service since it can be readily removed by disconnecting just a few cables.

HiQDT-CTRL-6CH six channel controller with 7.0”
touchscreen HMI shown with lid & swivel plate open with ethernet cable for remote access & MODBUST TCP.


  • Calibrations
    • Auto buffer pH calibration mode: 7.00 & 6.86 pH buffers for asymmetric potential (A.P.)
      4.00 & 1.68 pH buffers for acid slope plus 9.18, 10.00 & 12.45 pH buffers for alkaline slope o Manual calibration for pH/ORP sensors for process offset plus acid & base slope (pH only)
  • Analog Outputs
    • Up to 6 each isolated & scalable 4-20mA or 0-10VDC; software selectable for each channel
  • Contact Relays
    • Up to 18 each SPST relays rated up at 2A @ 230VAC or 30VDC for use as alarms or closed
      loop local control. Two (2) each relays assigned to process value per measurement channel.
  • Digital Input & Output
    • MODBUS TCP SLAVE (a.k.a. MODBUS over ethernet) for all registers on each sensor for
      every factory touchscreen controller to interface upstream PLC, SCADA or DCS if desired. o HiQDT controller is ALWAYS dedicated RS-485 MODBUS RTU master to HiQDT sensors
  • Datalogging
    • Large 32GB capacity to record all process values, analytic and calibration values over time o Remote access to logged data over FTP on local subnet, public IP or even behind firewall o Logged data can be converted to Excel for further workup and analysis of all channels
    • Date stamping on data using RTC for all factory supplied touchscreen HiQDT controllers

HiQDT-CTRL-2CH dual channel controller with 4.3” touchscreen shown in lid closed position. The 2 each HiQ4FP female panel mount connector are NEMA 6P rated waterproof hot-swap plug & play with the HiQDT sensors with the HiQ4M mal snap connectors.

HiQDT-CTRL-6CH six channel controller with 7.0” touchscreen shown in lid closed position. For the triple channel configuration there would exist only 3 each of the HiQ4FP female panel mount connectors. All packages are NEMA 4X pre-installed with all necessary cable glands ready for field use.

HiQDT-CTRL-2CH dual channel controller package with 4.3” touchscreen shown on top output side. HiQDT-CTRL-3CH/6CH three or six channel controller package with 7.0” touchscreen shown on the top output side.

Intelligent Monitoring & Troubleshooting of Installations without Site Visits:

  • Remote Access
    • Secure Maple Systems EZAccess 2.0 software offers complete remote graphical access to HiQDT controller with interface EXACTLY the same as if in front of touchscreen LCD. The remote access includes extensive security, tiered administration and access control features.
      • Windows PC Platforms as well as Android & iOS smartphones & tablets supported Email Notifications
  • Email Notifications
    • Email notifications for all logged events such as when a relay is turned on or off based upon setpoints for the process values or temperature or if a channel loses communication.
      • Proactive monitoring & support for installed sites even without using remote access

Selected Screenshots of Touchscreen Six Channel Controller

Default display with all other screens accessed through the main menu. Status updates, alarms & alerts are scrolled across the top of screen.

Main menu for main tasks & functionality of controller. Additional submenus load as needed to navigate the available features & options.

Measurement type for each channel on universal controller assigned or modified at any time using smart digital hot-swap plug & play sensors.

Sensor calibrations are displayed and datalogged including the time since calibration was last performed for best practice maintenance.

For six channel controller there is one analog output for each sensor, isolated, scalable & on-screen selectable as 4-20mA or 0-10VDC.

Analytic info for each channel shown & datalogged for details about not just process values but also the sensors used for the measurements.

High & Low relay process setpoints for each channel with time delay. Along with full secure remote access, email notifications are sent for each event.

Access to demo version of touchscreen controller is available for all configurations. Please complete the request form to receive the credentials & instructions to take a “Virtual Test Drive” of the advanced touchscreen controller software.

Tools for Setup, Configuration & Calibration with minimal work on customer PLC

  • Free of charge Windows software is provided with all HiQDT sensors to accomplish all user adjustable setup and configuration steps as well as calibration tasks.
    • ONLY the HiQDT Windows software can change the node address of HiQDT sensors o Create calibration certificate reports for archival quality assurance compliance and advanced analytics to optimize process maintenance as well as the sensor life cycle
  • Setup, configuration and calibration tasks can also be accomplished by a small compact lightweight battery-powered handheld communicator for HiQDT sensors if preferred.
  • This handheld communicator can also serve as a portable measurement system allowing industrial HiQDT sensors to be used both for spot analysis and troubleshooting in the field.
  • If desired the HiQDT Windows software and/or handheld communicator can perform all complex tasks meaning that only scaling of the process pH & ORP values & temperature readings is needed to commission HiQDT sensors in the field.

Zero Configuration Working Right out of the Box

  • Since the HiQDT MODBUS sensors are smart digital type they can be pre-calibrated to be ready to deploy right out of the box by simply plugging sensors in the mating keyed waterproof connector. Only requirement is to supply either AC or DC power as defined by the package type ordered.
  • The HiQDT sensors can be hot-swapped between different controllers with the only caveat that the MODBUS node address is valid for location to where it is connected (see installation guide).
  • Factory supplied packages can be pre-configured for matched node addresses on both the HiQDT sensors and mating controllers such that upon powering the equipment and plugging in the sensors it is immediately measuring and datalogging values.
    • All of this means that the HiQDT smart digital measurement system can offer TRUE ZERO CONFIGURATION working right out of the box which is ideal for situations where very fast commissioning is required or else when many installation points need to be started up in a narrow window of time.

Core Features for Smart Digital HiQDT Sensors

  • Store their configuration settings and all calibration values in the sensor allowing for complete portability in terms of where maintenance tasks such as cleaning and recalibration are performed.
  • Engineered process pH & ORP values sent are always calibrated and temperature compensated. Calibrated temperature and absolute mV values are also sent with (04) read_input_registers call.
  • In principle up to 247 HiQDT sensors can be installed onto a single RS-485 MODBUS RTU master, although it is recommended to use a repeater after 32 nodes (inquire to factory for assistance).
  • High speed MODBUS serial communications ensure low-noise operation in industrial process  environments at distances up to 1,000 meters (3,280 feet). Support for long cable runs allows for  installation of the mating controller to the HiQDT sensors at any convenient location at the site.
  • All smart digital HiQDT sensors standard with waterproof NEMA 6P rated quick disconnect snap connectors for convenient field commissioning and maintenance. Waterproof snap connectors  allow for seamless simple hot-swap plug and play functionality with mating PLC controllers.
  • Portable battery powered handheld communicator for portable spot measurements using same HiQDT industrial sensors used for continuous inline field measurements ensuring reliability of  results whether the analysis if done by periodically dropping the sensor into the tank as a submersible or from the inline sensor that is tied into the main SCADA, PLC or DCS.
  • Very fast booting HiQDT sensors have readings ready to view or record in as little as 2 seconds.
    • Ideal for intermittent operation from dataloggers or else spot portable field measurements.

Capabilities of Smart Digital HiQDT MODBUS pH & ORP Sensors

  • Supported pH Range from -2.00 to +16.00 (Max Resolution 0.001pH unit)
    • Actual pH range for particular sensor model is defined & limited by specifications
  • Supported Standard Range ORP Mode from -1,000 to +1,000 mV in (Max Resolution 0.1mV) o Raw Absolute mV Resolution 0.05mV for pH or Standard Range ORP Modes
  • Supported Wide Range ORP Mode from -2,000 to +2,000 mV in (Max Resolution 0.2mV) o Raw Absolute mV Resolution 0.10mV for Wide Range Range ORP Mode
  • Inline Installations up to 150 °C Maximum Temperature & Maximum Pressure 200 psig
    • Fully Submersible Installations up to 125 °C max (if sensor is rated to at least 135 °C)
    • Inline max temperature for particular sensor model is defined & limited by specifications
  • Minimum temperature -35 °C for Extreme Dehydration Resistant Series (Inline or Submersible)

Calibrations Features for Smart Digital HiQDT Sensors

The smart digital HiQDT pH & ORP sensors integrally store these calibrations which are used to compute and send calibrated and temperature compensation pH, ORP and temperature values. The time in service since each calibration type was last performed is stored for analytic purposes.

  • Temperature Offset for both HiQDT pH & ORP sensors
  • mV Offset for HiQDT ORP sensors
  • Asymmetric Potential (Offset) for HiQDT pH sensors
  • Acid Slope for HiQDT pH sensors (used when media measured is less than pH7)
  • Alkaline Slope for HiQDT pH sensors (used when media measured is more than pH7)

    Factory HiQDT Controller has autobuffer pH calibration: 7.00 & 6.86 pH buffers for asymmetric potential (A.P.) 4.00 & 1.68 pH buffer for acid slope & 9.18, 10.00 & 12.45 pH buffer for alkaline slope

Core Setup, Configuration & Analytic Features for Smart Digital HiQDT Sensors

  • The smart digital HiQDT pH & ORP sensors store the following core and analytic information:
  • Type - pH or ORP
    • Note: Dual pH/ORP all-in-one configurations are considered as two separate HiQDT sensors from a configuration setup point of view with each parameter having its own node
  • Baudrate – 9600 or 19,200 kbps
    • Note: All sensors on MODBUS network must have same baudrate
  • Node – User adjustable from 1 to 247 – Max HiQDT sensors on one network, use repeater after each 32 HiQDT sensors; See HiQDT installation guide & controller manual for best practice setup
  • Temperature Compensation Coefficient – Default is classical 0.198mV per °C Nernstian value o Adjustable temperature compensation from 0.000 to 0.999 mV for special applications
  • Smoothing dampener for process readings (time averaging) – From 1 to 30 seconds
  • Delay from boot to send values (important setting for intermittent battery powered operation)
  • Sensor Item Number (Discrete Coding for Exact Configuration & Options)
  • Serial Serial Number (for Complete Traceability back to Factory)
  • Max (up to 210°C) & Min (down to -40°C) Temperature in Service (when sensor is energized)
  • Total Days in Use
    • Incremented for each hour sensor is continuously energized. Stored in units of hours with a max value of 7.5 years. The native units of total hours in use is typically converted into units of total days in use for ease of viewing and evaluation.
  • Software Revision of Board - for support purposes and troubleshooting
    • HiQDT sensor boards can be flashed in the field if necessary with updated software

Installation Configuration Available for Smart Digital HiQDT Sensors

  • The entire line of built-to-order IOTRON and ZEUS pH & ORP sensors with all possible configurations and options available smart digital HiQDT style. Support for all inline & immersion and fully submersible installations, twist lock quick disconnect bayonet style installations as well as sanitary and HOT-TAP valve retractable installation schemes.
  • Smart digital HiQDT sensors are available in single parameter configurations where just pH or just ORP is measured as well as in dual pH/ORP all-in-one configurations where both pH & ORP parameters are measured in one sensor.
    • Dual pH/ORP smart digital HiQDT sensors require suitable waterproofing sealing option for space needed for 2nd sensor board to measure two parameters in a single sensor.

Special order requests are considered on a case by case basis for feasibility of implementation.

  • Built upon the foundation of robust Maple Systems HMI & PLC, the HiQDT controller can be purchased in customized hardware configurations such as additional outputs or relays as well as integrating other non-liquid analytical functionality (flow, level, temperature, pressure, etc.)
  • Unused hardware can be implemented for custom software functionality. For example:
    • Anywhere from 2 each to 4 each scalable analog inputs are unused and available for use in
      custom software implementation to assimilate other measurement parameters if desired.
  • Additional software features and functionality may be added as special order option.
  • Special order requests are considered on a case by case basis for feasibility of implementation.
    • If special hardware configuation and/or software features & functionality request is feasible then some type of Non-Recurring Engineering (NRE) and/or minimum order quantity (MOQ) may exist for each such special order package.

Compatibility of HiQDT MODBUS sensors & 3TX Transmitters with MODBUS

  • The HiQDT pH & ORP sensors can be used on the same RS-485 MODBUS network as the 3TX transmitters with the RS-485 MODBUS RTU communication option. In this way any existing analog pH, ORP, conductivity, dissolved oxygen (DO) and ion selective (ISE) sensors interfaced with 3TX-pH, 3TX-CON, 3TX-DO or 3TX-ISE transmitter (respectively) can share the MODBUS network for sending the process values together with HiQDT MODBUS sensors.
  • Only the usual caveats apply such as all nodes having the same baudrate and that a unique node address must exist for each device. Whereas the badurate and node address can be changed from the display on the 3TX transmitter the baudrate and node for the HiQDT sensors can only be changed with the provided free of charge Windows HiQDT setup and calibration software.
  • The intelligent digital 3TX-HiQ-pH transmitters interfaced to the smart digital HiQ pH & ORP sensors can also share the same MODBUS network as the smart digital HiQDT MODBUS sensors as well as the 3TX transmitter with MODBUS output option.
  • Free Windows Datalogging & Graphing software can log process pH/ORP, temp. & absolute mV values from any HiQDT pH & ORP sensors on same modbus network as 3TX transmitters.
    • Windows Datalogging & Graphing Software is an excellent commissioning tool to test all devices on MODBUS network are functioning correctly before connecting to the main PLC.