Xylem H-3531 FlashLite - Manual (Page 17)

H-3531
Installation 2-5
initiated and the H-3531 FlashLite™ waits for a command from the menu for 3 minutes
and then times out.
2.4.3 Quadrature Output
Pins 1 and 2 of the main interface connector are for simulating a quadrature shaft encoder
output. The user can enable this option by sending the appropriate SDI-12 command or by
using the simple RS232 menu interface as explained in section 4.3.5/5.12. The quad
output uses signals Phase A and Phase B and is updated every new measurement. The user
can also put the H-3531 FlashLite™ in power mode 3, which is a continuous loop mode
that causes the H-3531 FlashLite™ to update the quadrature output at a user defined rate
which is the measure rate(see section 5.17).
2.4.4 0-5 Volt Analog Output
Pins 3 and 4 of the main interface connector are for outputting a 0-5V analog signal based
on the stage. This is also an option that the user must enable by sending the appropriate
SDI-12 command or by using the simple RS232 menu interface as explained in section
4.3.12/5.13. This output is also only updated following a new measurement. The user can
put the H-3531 FlashLite™ in power mode 3, which will update the 0-5V output based on
the measure rate.
2.5 Industrial Mode
When the user orders the H-3531 FlashLite™ the user must specify industrial mode if 4-20mA
output, Modbus/H-355 bubbler control is desired, otherwise the user must send the H-3531
FlashLite™ back to Design Analysis Associates to change to industrial mode.
2.5.1 4-20mA Output(Industrial Mode Only)
Current loop sensors output a current rather than a voltage. The 4-20mA output will drive
standard industrial telemetry and process control instrumentation. Since the signal to
noise margin of 4-20mA is not large, take care to protect the wiring from noise and
interference. The loop power supply must be sufficient to maintain 8.5 to 35V across the
H-3531 FlashLite™'s output wires, in addition to whatever voltage is needed to maintain
20mA across the loop receiver and interconnect wiring. The +12.0V SDI-12 power source
will work only if the resistance of your loop receiver and wiring is less than 150 ohms.
8.5V + (150ohms * 20mA) = 11.5V
The 4-20mA output is reverse diode protected. The H-3531 FlashLite™ is not loop
powered, continuous +12V instrument power must be supplied via the 7pin circular
connector.
! Make certain there is 8.5 to 35V across the 4-20mA output wires.
! Make certain the H-3531 FlashLite™ is receiving +12V power.
! Use shielded 4-20mA cables in noisy environments.