1. DESCRIPTION
The BA358E is a panel mounting intrinsically safe
4/20mA loop-powered Rate Totaliser primarily
intended for use with flowmeters. The instrument
simultaneously displays the rate of flow and the
total flow in engineering units on two separate
displays. The BA358E only introduces a 1.2V
drop, which allows it to be installed into almost any
4/20mA flow loop. No additional power supply or
battery is required.
The rate totaliser has been certified intrinsically
safe for use in gas and dust hazardous areas by
Notified Body Intertek Testing and Certification Ltd
and complies with the European ATEX Directive
94/9/EC. The EC-Type Examination certificate
specifies that under fault conditions the output
voltage, current and power at the 4/20mA input
terminals will not exceed those specified for
simple
apparatus
in Clause 5.7 of EN 60079-11, which
simplifies installation and documentation.
For international applications the BA358E has
IECEx, FM and cFM certification which are
described in Appendixes 2 and 3.
2. OPERATION
Fig 1 shows a simplified block diagram of a
BA358E. The 4/20mA input current flows through
resistor R1 and forward biased diode D1. The
voltage developed across D1, which is relatively
constant, is multiplied by a switch mode power
supply and used to power the instrument. The
voltage developed across R1, which is proportional
to the 4/20mA input current, provides the input
signal for the analogue to digital converter.
Each time a 4/20mA current is applied to the
instrument, initialisation is performed. After a short
delay the following display sequence occurs which
takes about twelve seconds:
All segments of the display are activated
Loading message displayed
Configuration message displayed
Model and firmware version displayed
The BA358E Rate Totaliser starts
functioning, using configuration information
stored in the instrument’s permanent
memory. Unless total and grand total
displays have been reset to zero, new flow
will be added to the existing totals.
If the 4/20mA current is disconnected during
operation the latest total and grand total are stored
in permanent memory.
Fig 1 Simplified block diagram of BA358E
2.1 Controls
The BA358E is controlled and calibrated via four
front panel push buttons located below the display.
In the operating mode i.e. when the instrument is
displaying rate and total flow the push button
functions are:
Summary of Push Button Functions
P
Displays input current in mA or as a
percentage of span. Modified when
optional alarms are fitted.
▼
Shows rate display calibration at 4mA
input.
▲
Shows rate display calibration at
20mA input.
E
Shows time since instrument was
powered or total display was reset.
E+▼
Grand total –
displays least significant 8 digits
E+▲
Grand total –
displays most significant 8 digits.
▼
+
▲
Resets total display
Configurable function
P+▼
Shows firmware version
P+▲
Alarm setpoint access
Configurable function
P+E
Access to configuration menu
3
