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The Tracker 240 series of Digital Panel Indicators are designed specifically for use with load cell transducers and for weighing applications. All the Tracker 240 series models have a 5-digit display and transducer supply plus many software features including tare, offset zeroing, in-flight compensation, peak picking and extensive alarm functions. As standard, the Tracker 240 series are fitted with an analog output and an RS422/485 communications interface to allow connection to data loggers, chart recorders, PLCs and computers. All models have the same specification except that the T244 has 2 relay outputs to control external devices and the Tracker 245 has 4 TTL logic outputs. The displayed value can be in tonnes, litres, grams or any other engineering unit. The Tracker 240 series can be used in conjunction with up to 4 x 350Ohm load cells, and uses a 6-wire ratiometric measurement technique. Power for the load cells can be provided from the internal or an external supply.

Transducer Excitation Supplies
10V DC (or 20 volt DC for use with I.S. barriers) fully drift compensated.

6-Wire Ratiometric Input
For maximum measurement precision.

Sensor Connections
The Tracker 240 series use a 6-wire ratiometric method of measurement. Up to 4 x 300Ohm load cells can be connected in parallel. More can be used if the resistance is higher (e.g. 8 x 700Ohm load cells) and the total current does not exceed 120mA at 10V DC An external 10V DC supply can be used, if required, still retaining the ratiometric measurement capability.

Analog Output
The user programmable analog output allows the Tracker 240 series to transmit the measured display value or the maximum, minimum or average, or a value sent via the serial interface. The analog output can be scaled for any portion of the display range and is configurable for 4-20mA, 0-20mA or 0-10 volt signals. Electrical isolation ensures that problems with earth loops are avoided.

Calibration Scaling and User Linearization
Calibrating the Tracker 240 series to load cells can be achieved in one of two ways. Values from the strain gauge can be entered manually or the Tracker can read the actual output from the transducer at 2 points in the range, normally at zero and another point near the maximum load to be measured. These measured values are stored with their associated display values as the calibration parameters. For more demanding applications, up to 8 points can be independently calibrated to compensate for any non-linearity from the load cell.

Display
The user can configure the Tracker 240 series for the required engineering units and display resolution. The resolution is user configurable for 1, 2, 5 and 10 digits. This can be useful if a steady reading is difficult to achieve. Normally the full resolution would be displayed. For noisy signals an independent display filter is provided. The user can select the display update rate to be 2, 4 or 10 per second, and the brightness can be adjusted to suit ambient lighting conditions.

Smart Filter
Often plant vibration can effect the measured values and make the display appear "noisy". The Tracker 240 has a smart filter that samples the "noisy" signal from the load cells and then calculates a filter band value. When in use, the filter is only applied when the measured value rate of change is within the filter band. To allow a fast response for real change of signal the filter is turned off until the signal rate of change is again within the filter band limits.

Digital Status (Logic) Inputs
Two logic inputs are provided to allow remote control of the Indicator functions via external devices such as switches or PLCs. Volt free contacts or open collector TTL outputs may activate the inputs. The 2 inputs can be individually programmed by a user to perform one or more of the following functions:

• Tare
  
• Zero
  
• Part Count
  
• Display Hold
  
• Display Maximum (Peak)
  
• Display Minimum (Valley)
  
• Display Average
  
• Display Reset (Peak Picking Mode)
  
• Display Test (Lights all Display Segments)
  
• Keyboard Lock
  
• Alarm (Latch) Reset
  
• Alarm Disable
  
• Analog Output Hold
  
• Reset Max, Min and Average
  
• Start Fill

Front Panel Function Keys
The 5 front panel buttons can be used to set up a unit by stepping through a simple password protected menu. In addition, the 2 front panel function buttons can be individually programmed by a user to give operator level access to one or more of the following functions:

• Tare
  
• Zero
  
• Part Count
  
• Display Hold
  
• Display Maximum (Peak)
  
• Display Minimum (Valley)
  
• Display Average
  
• Display Reset (Peak Picking Mode)
  
• Reset Max, Min and Average
  
• Display Test (Lights all Display Segments)
  
• Start Fill

Alarm Menus
Alarms can be flashed on the display along with the measured value. The user can individually configure the following parameters for each of the 4 alarm menus:

High, Low or Deviation Alarm Action

High and Low Band Limits (Deviation Action only)

On and Off Delay Timers

On and Off Hysteresis

Latching or Non-Latching
Normal or Pulsed Output Modes

Setpoint Adjustment (during normal running or only via password protected menus)

When Filling Modes are selected, Digital (TTL/ Relay) Outputs 1 and 2 are automatically assigned.

Serial Communications
The Tracker 240 series are equipped with an isolated RS422/485 serial communications interface to allow connection to computers or PLCs. Three protocols are provided as standard to allow easy integration with most SCADA packages. The user can also select Master Mode to allow digital transmission to a remote repeater display or printer. Consult your supplier if your require RS232 instead of RS422/485. The combination of a Tracker 240 and an HMI, fitted with a Modbus compatible RS485 interface, becomes a powerful stand-alone batch control system and recipe selection system. The HMI's display and function buttons can be tailored for any application and language. Many HMI units can also be a gateway for Fieldbus connection (e.g. Profibus, Device Net). A single HMI can communicate with up to 32 Tracker 240 units.

Universal Power Input
Wide-ranging 90-265V AC input allows world-wide installation. A low voltage 24V AC/DC input option is available.

Tough but Attractive
The enclosure uses flame retardant (VO) materials and the front panel conforms to IP65. The plug in sleeve type construction facilitates simple exchange for routine servicing / calibration.

Clear Display
The flat recessed 5-digit display, together with high brightness red or green LEDs ensure maximum visibility even in difficult ambient lighting conditions.