pH MEASUREMENT & CONTROL USING THE ACC SERIES

pH is an important parameter to monitor and regulate in many process involving acid and base reactions. The ACC Series controller pH sensor input module enables standard pH sensor outputs to be measured directly. pH recalibration may be easily performed by the built-in single and multi-point calibration functions using standard buffer solutions, or other suitable process procedures.

pH reagent dosing is directly controlled using the specially developed ACC pH control algorithm which may be programmed to automatically repeat on a pre-programmed OFF/ON-time. After a preset time interval, pH is checked (OFF-time) and if reagent is required to maintain the specified pH range, a programmed (ON-time) amount of the reagent (acid or base) is added. The cycle continues until the process is maintained to correct pH range.

Additional functions that may be easily added include: pH data logging, dosing reagent, low tank level warning alarms and pH out of range alarms. This information may be presented on either a numeric or graphic LCD display and transmitted to a supervisory system by serial or Ethernet communication.

• RTD input for temperature compensation.
• pH control and alarm functions.
• Automatic overdosing compensation for variable reagent flow rates.
• Event and sequence outputs for sensor retraction and calibration.

ELECTROCHEMICAL REACTION RATE CONTROL USING DC CURRENT FOR PLATING AND CHEMICAL PROCESSING APPLICATIONS

Electroplating and electro-chemical process reactions are maintained by controlling the current flow within the electro-chemical cell. Using the ACCs direct current measurement module and current control optimized PID algorithm, consistent plating results are easily achieved. Typical electroplating control and alarm configurations include:

• Plating current display in Amps from a DC shunt
• Display and control from totalized amp/hrs
• Process time remaining display
• Plating solution concentration display and automatic replenishment control

PRODUCE WEIGHING APPLICATION

Grading, packing and distribution facilities must determine the quantity of produce they have received from producers in order to calculate pricing and producer payments. Produce is delivered in large bins which are loaded onto a conveyer and transferred to a weighing platform. The bin is automatically raised to the weigh position, after a delay for the weighing platform to stabilize, the bin is weighed. The bin then raises and tips the produce onto a grading conveyer feed hopper. The bin then returns to the load cell weigh position and stops. The process is repeated with next load.

The ACC Series controller tares the empty bin weight. The result is the produce weight. The bin number is counted. The produce weight is added to the total fruit weight and the average fruit weight per bin is calculated. A serial printer connected directly to the ACC controller RS-232 serial port prints a receipt detailing the time and date of receipt, number of bins, total produce weight and average produce weight per bin received.

• Uses a graphic display for improved operator instruction and legibility
• RS-232 output to computer for analysis and production records.

WEIGHT AND RATIO BATCHING

Many industrial chemical processes require substances to be accurately batch blended to a specified composition ratio. This application describes how varying amounts of primary and secondary materials may be automatically mixed to a predetermined ratio.

Using the ACC Series controller and load cell input module the quantity of secondary material to be blended with a primary material is calculated using an ACC macro function. This macro also compensates for varying material densities, enabling both volumetric and mass based blending.
The weighing platform is tarred with the mass of the blending container. The tarred container is partially filled with primary product. The operator enters the required mix ratio and presses the blend start button. A pump feeds secondary material into the container. When the secondary product nears the calculated mix weight ratio, the ACC PID control output reduces the blend pump motor speed until the calculated weight is reached. The pump then stops. The display indicates when the process is complete, the blend ratio, and the weight and volume of the blended product.

• Automate completion of process.
• PID-OFF control. Secondary solution pump.

TANK LINEARIZATION APPLICATION

An ACC Series controller uses a level sensor to continuously monitor the volume of fluid in an irregularly shaped tank. Since the output from the level sensor is non-linear, an ACC Series controller is used to linearize the signal. The digital display shows the amount of fluid in liters and consumption in l/hr. The actual volume of the tank is calculated for the most non-linear areas of the tank and these are entered into the controller. Limit alarms are configured to indicate when the tank is 20% and 10% full.

• Calculate and display liters per hour derived from a flow sensor input

PRECISION LOW RESISTANCE MEASUREMENT WITH TEMPERATURE COMPENSATION

An ACC Series controller/indicator can be used to measure the resistance of hot copper coil windings,
which is required for quality control reasons. A constant current is passed through the coil and the resistance calculated. To compensate for temperature variation an infrared pyrometer temperature sensor monitors the coil temperature. A band alarm is used to indicate 'PASS' or 'FAIL' of the coil under test. The meter's decimal point is set for a display resolution in milliohms (0.001 W). The meter can be configured with temperature compensation for almost any conducting material.

• Print labels.
• Auto sample, log and print for quality control records.
• 0.0001W resolution.

IRRIGATION SCHEDULING CONTROLLER

Successful crop yield often relies on the effective management of available water resources. Controlling crop irrigation by monitoring and responding to rainfall variations assists in maximizing crop yield while reducing irrigation costs.

A weather station is easily connected to a ACC Series controller using an ASCII communication connection, providing economic measurement of rainfall and weather related growing parameters such as: solar radiation, wind speed, and air temperature. A macro calculating daily evaporation determines the quantity of water required for effective irrigation and schedules delivery according to ambient temperature and time. Using the built in ACC data logger function, it is possible to monitor and record environmental conditions and irrigation delivery. Remote monitoring of the irrigation system status and climatic data is provided using a convenient and cost effective GPRS modem connection. GPRS modem information is available as either; SMS text, E-Mail or on a remote web server host.

SMOKE DENSITY AND TEMPERATURE MONITOR

Legislation limiting the maximum flue-gas smoke density is now enforced in most areas. Authorities often require flue-gas output opacity (smoke density) and temperature to be monitored and recorded at fixed time stamped intervals.

The ACC Series controller is easily configured to monitor and display averaged opacity and minimum temperature readings. Using the built in ACC SD RAM card based data logger function, it is possible to securely store these readings on a fixed time base and download them directly to a serial printer or a centralized host device via an industrial communication protocol such as ModBus RTU, DeviceNet or Ethernet TCP/IP. SD RAM card data may also be directly downloaded to a PC host using a smart media interface adaptor.

FLOW RATE AND TOTAL FLOW MEASUREMENT

Paddlewheel and turbine flow sensors provide an economic and reliable method of measuring fluid flow. Both methods are similar in operation, relying on the energy in the flow stream to spin a rotor, generating either a sinusoidal or square wave output. Most paddlewheel and turbine flow sensors use rotors with magnets embedded in each blade. The magnets are used together with a coil or Hall effect sensor to produce the sinusoidal output. This is used to trigger an electronic switch which produces a square wave output. Instrument interface is normally provided as an open collector connection. The resultant frequency is directly proportional to the flow rate.

The ACC Series universal frequency/counter input module interfaces with most pulse output sensor signals directly, providing a reliable, cost effective solution for flow, totalizing, and flow monitoring/control applications.