Radio Frequency Capacitance Type Level Switch

Capacitance level detectors are also referred to as radio frequency (RF) or admittance level sensors. They operate in the low MHz radio frequency range, measuring admittance of an alternating current (ac) circuit that varies with level. Admittance is a measure of the conductivity in an ac circuit, and is the reciprocal of impedance. Admittance and impedance in an ac circuit are similar to conductance and resistance in a direct current (dc) circuit. In this chapter, the term capacitance level sensor will be used instead of RF or admittance.

Probe Designs : The most common probe design is a stainless steel rod of in. or 1/2 in. diameter, suitable for most non-conductive and non-corrosive materials. The probe is insulated from the housing and bin wall by an low-dielectric insulator, such as Nylon or Ryton. These polymers have maximum operating temperatures of 175-230°C (350-450°F). Ceramics can be used for higher temperature applications or if abrasion resistance is required. For applications where the process material is conductive and corrosive, the probe must be coated with PFA or Kynar.

Some point level sensors are available with build-up immunity, or coating rejection functionality. This is required when the process material is wet or sticky and likely to cause permanent coating.

Radio Frequency based level switches have been designed, based on the physical & chemical properties of material (solid or liquid), process temperature & pressure, etc.

Sticky materials like Coal - Tar, Furnace Oil, etc. accumulate over the sensing probe. RF Type level switches remain unaffected due to such accumulation. It easily works on Acid, Cement, Oil, Polyester, Plastic, Coal Tar, Fly Ash, Slurries, Milk, Sugar, Sewage, Steel Plant, Tooth Paste, Medicine, Filter Choking, etc.

Electronics & Housings :
The electronic circuitry of the probe performs the functions of:
1. Rectifying and filtering the incoming power
2. Generating the radio frequency signal
3. Measuring the changes in current flow
4. Driving and controlling interface devices such as relays, analog signal generators and display meters.

The circuitry is usually of solid state design and provided with potentiometer adjustments for setting sensitivity and time delays.

Because the level sensor will ultimately drive an external device, it is advisable to evaluate for system compatibility the number of relays required, their capacities, or the analog signals required, time delays, and power supply requirements. More advanced microprocessor-based units are self-calibrating; sensitivity and time delay adjustments are under pushbutton control. These units are often supplied with self-test capability and built-in temperature compensation.

HYDROtECH Ultrasonic Liquid Level Indicator

JAC-ULS500 is an ultrasonic level sensor for accurate measurement of distance between sensor and obstruction. It is highly suitable for applications such as measurement of fuel or any liquid level in a tank. It is also suitable for applications requiring linear distance measurement such as linear guides.

The level sensor works on the principal of distance calculation by measuring the duration between travel of sound wave emitted from the sensor and the subsequent echo received. The speed of sound is corrected for temperature variations using built-in temperature sensor. The device is factory calibrated and tested with no general need for on-site calibration.

JAC-ULS500 level sensors are small in size and low cost making them ideal for OEM applications. These sensors can tolerate harsh environments such as factories, plants and construction and render outstanding performance over wide temperature conditions. These devices find applications in power, chemical plants, automotive, marine, robotic and automation industry.

It works perfectly within the range of 0 – 10 meters. The frequency of the Transducer is 40 KHz. The display is Digital (7-segment LED).

HYDROtECH Wireless Data Transmission System

A set of Transmitter & Receiver is used for wireless data transmission which operates on FM / Radio Frequency.

This device has two push buttons to control the operation of remotely located motor, valve. It transmits control signals to receiver located at remote site. The transmitter operates at 2.4GHz frequency band which is a free band for industrial applications. Following are the specifications of the transmitter.

. Operating range: 500m (outdoor)
. User interface: Two push buttons with LED for visual indication
. Power supply: Onboard battery
. Operating frequency: 2.4GHz

The receiver has two relay outputs to operate motor and valve. It receives control signal from Transmitter on 2.4GHz frequency. Following are the specifications of receiver.

. Output: 4 NO, 4NC (4 relays)
. Operating frequency: 2.4 GHz
. Power supply: 230VAC

REPEATER This is signal booster device to increase the range of wireless operation.
. Power supply: 12VDC , 230VAC, Onboard battery (optional)
. Indications: LED display for battery power indication

Remotely Controllable Water Pumping Stations (GSM)

JOHNSON's Pump Station Automation System is Remote Control and Maintenance solution for wastewater pump stations. JOHNSON's PSA controls water pumps to maintain water level within normal limits. System detects variety of abnormal pump station conditions and sends alarm messages immediately to Internet SCADA and to service men's GSM (Mobile) phones.

When water level exceeds the defined high level limit, the pump station is commanded to stop pumping. System calculates the pump's efficiency curve, which can be analyzed in the internet SCADA view. The efficiency curve shows situation when pump is slowly jamming or wearing.

JOHNSON's PSA (Pump Station Automation) Pump efficiency factors are calculated in PSA. Decreasing efficiency factors can be seen in the SCADA's trend diagrams. Service man can be send on-site to check the pump status.

Pumps operation times and counts can be analyzed in SCADA's diagrams. Abnormal situations can be seen. Using the pump's power consumption factor, approximate power consumption and costs can be calculated. Energy consumption can be calculated accurately if the pumping station is equipped with energy meter with pulse output or modbus interface. Diagrams can be seen in SCADA. Alarms are send immediately to SCADA and can be forwarded automatically to on service man's GSM-phone or e-mail or TROUBLE TICKET maintenance work system.

User can login to the system with normal Web browser to see alarm, diagrams, trends, process views, print reports etc. from any PC or from Internet capable Mobile phone.

From the pumping station HMI display, service man can check the water level, pumps operating counts & times and possible abnormal situations. Service man can set pumps start / stop / alarms levels from the HMI or SCADA (Web browser). JOHNSON's Pump Station Automation System Internet SCADA works everywhere. The previous pump is controlled to stop pumping if the water level increases to the high level limit. Communicates using GSM / GPRS networks.

Alarms and maintenance reports to/from GSM phone

Map view
. Pump stations status can be seen on the dynamic map.

Alarm view
. All active alarms in the same view, pump station alarm views
. Alarm acknowledgement
. Alarm history reports
. Intelligent alarm forwarding to on duty serviceman's gsm or e-mail.

Bar-graph and trend diagrams
. Fault diagnostics and reports
. Days min/max values
. Hourly averages
. Pump efficiency bargraph curve
. Pumps operating counts & times day, week, month, year diagrams.
. Power consumption day, week, month, year diagrams
. Flow rates day, week, month, year diagrams
. All information can be read to EXCEL for own reports etc.

Server Setup
JOHNSON's PSA is hosted Internet "control room" service for remote target supervision and control. Server is hosted (24/7/365). Customer doesn't need to participate on server PC investments or maintenance tasks!

JOHNSON's PSA service collects measurement and status data from remote targets via GSM / GPRS network. Data is stored to PSA's database.

Collected data can be analyzed using normal web browser. User (s) just logs in to the secure PSA web pages and after few clicks user can see status of their remote targets, print monthly reports, analyze productivity, check maintenance.browse alarm views, trend views, process picture views, target control views, report views, trouble ticket views...

Full control, anytime -anywhere !
Instant alarms directly to right persons! JOHNSON's PSA can send alarm messages immediately to service men's GSM phones and/or e-mails and reach the person whether he is on the field or behind his desk.

JOHNSON's PSA has all the information about the configured users, user groups, GSM-RTUs, I/O points, analog input scalings, allowed phone numbers, etc. Authorized user can maintain complete system remotely using the Web browser.

Configuration parameters
. Can be set remotely using Web browser or GSM phone.
. Pumps start / stop / alarm levels, alarm delays
. Servicemen's gsm phone numbers and e-mail.
. Fault diagnostic alarm set points and energy consumption factors
. Continuous pumping alarm time
. Max pumping count / day alarm limit

JOHNSON's GSM-Control Units

JOHNSON's Control Pump is complete solution. It is not only supervision software, it also includes JOHNSON's GSM control units. Control units are installed along with monitored targets.

Inputs & Outputs (I/O)
In typical application control units are connected to targets to measure different kinds of analog values, like temperatures, pressures, surface levels, voltages, currents etc. and digital ON/OFF status information. Control units have also digitaland analog outputs.

GSM control units have selectable analog input modules for all standard measurement ranges (0-20mA, 4-20mA, 0-5V, Pt100, RMS Voltage, RMS Current etc.) so almost any sensor in the market can be connected to control unit. In addition control units have free serial port which supports Modbus RTU protocol, so it can communicate directly with other control units, SCADA systems or intelligent meters / actuators etc. 

Control program (Application program)
Target applications can be controlled automatically using the control unit's control program or manually from the Control Pump Web interface. Normally control unit can handle all the needed automation tasks so no other automation devices are needed.    Control unit is Programmable logic controller (PLC) which means that user can write control program which is capable of doing demanding automation tasks like PID controlled positioning, real-time-clock based controlling, measurement processing, averaging, filtering, arithmetic, fault diagnostics, alarm generation etc.

Data logging
One typical task for control unit in many applications is to log measurement data into its memory. Control unit is capable of storing for example 16 measurements with time-stamp in one minute periods for 7 days. Stored log can be send to Control Pump server using GPRS data transfer. This allows that control unit doesn't need to be on-line all the time in order to send measurement data to server. This is important especially in low power applications.

Alarm generation
Control unit can generate alarms when a measurement goes below / above defined alarm limit or e.g. by combining many conditions (diagnostic alarms). Alarm is time critical information and it can be send immediately to server, from where it can be forwarded as text GSM/SMS message or e-mail to defined (on-duty) service man.

Other Features
Control unit has many other useful features like: remote programmability via GSM network, RS232/RS485 Modbus master/slave connection to other systems, connection to JOHNSON's HMI front panel, real time clock and calendar which can be used to make time based controls, connection to JOHNSON's wireless Wi-Fi sensor network (WSN) I/O modules etc,

TECHNICAL FEATURES (GSM Transmitter & Receiver)
  • Dual/Tri* band GSM 900/1800/1900 MHz
  • Data, SMS (Text & PDU), Fax, Voice* and GPRS (Class 10)
  • Variable DC input voltage
  • Fully compliant with ETSI, GSM Phase 2+ specifications
  • Low power consumption
  • AT Commands
  • 1.8V and 3V SIM Interface
  • RS-232 interface (9 PIN 'D' type female)
  • Complies 6KV surge protection

Remote Operational Features:
  1. Working Principle: GSM Based, SMS cum Dialing Service
  2. Firstly SMS will be send. If it doesn't acknowledge within 30 seconds from the receiver, then dial service will be initiated automatically. The indication will be displayed on the Remote unit thru LED's.
  3. During Dialing process, LED will indicate its confirmation.
  4. Push Button has been provided for Valve ON & OFF.
  5. It indicates the current status of Valve i.e., ON / OFF.
  6. The unit is powered by Li-ion Rechargeable Battery 14.8VDC, 1500mA-h.
  7. Battery Charger will also be provided.
  8. Battery charging status has been displayed with the help of Multi color LED's.
  9. Green LED indicates "Full", Yellow indicates partly charged while Red indicates "Empty".
  10. Housing: ABS Plastic
  11. Light in weight, Durable, Tough & small in size.
  12. Power ON / OFF Button. During OFF position, battery will be disconnected.