Description

The new BA304D is a third generation intrinsically safe field mounting indicator housed in a robust IP66 GRP enclosure incorporating a separate terminal compartment and dedicated access to the instrument controls. Retaining all the features of the popular BA304C, this new indicator provides improved display visibility, plus simplified installation, calibration and routine inspection facilities. Like its predecessor, the BA304D displays the current flowing in a 4/20mA loop in accurate engineering units. The instrument is loop powered but only introduces a 1V drop allowing it to be installed in series with almost any 4/20mA loop.

Main application of the BA304D is to display a measured variable or control signal in a hazardous process area. The zero and span of the display are independently adjustable so that the indicator can be calibrated to display any variable represented by a 4/20mA current, such as temperature, pressure, level or actuator position. When used with a differential flow transmitter an optional square root extractor enables the BA304D to display flow in linear engineering units. The enclosure which is moulded in glass reinforced polyester (GRP), has stainless steel fittings, silicone gaskets and an armoured glass window. Its robust construction provides IP66 protection which has been independently assessed by ITS - report available.

A separate terminal compartment allows the instrument to be installed and terminated without exposing the display electronics. To further simplify field wiring and subsequent inspection, the terminal cable entries and the clamping screws are both forward facing. Additional terminals are provided which may be used to link the return 4/20mA conductor and the cable screens. A separate sealed cover provides access to the plug-in calibration links and potentiometers without exposing the display electronics or field terminals International intrinsic safety certification allows the BA304D to be installed throughout the world. The 4/20mA input terminals comply with the requirements for simple apparatus enabling the indicator to be connected in series with most certified intrinsically safe circuits; together with the low voltage drop, this makes the instrument very easy to apply. ATEX, FM and cFM approvals permit installation in Europe, USA and Canada and IECEx certification allows installation in a growing number of countries including Australia and New Zealand.

Two alternative backlight options are available. The loop powered backlight produces green background illumination enabling the display to be read at night and in poor lighting conditions. It does not require an additional power supply, IS interface or field wiring, but the indicator voltage drop is increased. The separately powered backlight provides a bright orange output to enhance daylight viewing, but it requires an additional IS interface and field wiring.

An optional internal calibrator simulates a 4 and 20mA input current so that the indicator may be recalibrated without the need for test equipment or disconnection from the 4/20mA loop. Although not providing independent verification, it is an effective way to quickly check performance or to recalibrate. Units of measurement and the instrument application or tag number can be economically marked onto the display escutcheon prior to despatch or after installation on-site. Alternatively, for customers who prefer an etched stainless steel label, the indicator can be supplied with a removable blank or custom etched stainless steel plate mounted on the front of the instrument. Reliability is ensured by an ISO9001 approved quality control system supported by a three year guarantee.

The BA304D is protected from reverse connection and overrange input currents and incorporates extensive radio frequency filtering to comply with the European EMC Directive. The indicator assembly can be removed from the enclosure without disconnecting the field wiring or disturbing the 4/20mA loop, continuity being maintained by a diode within the terminal assembly.