Vaisala DMT152 - Manual (Page 24)

User's Guide _______________________________________________________________________
22 ___________________________________________________________________ M210865EN-F
Power Supply Requirements
The DMT152 transmitters are designed to operate with a supply voltage
of 15 ... 28 VDC (voltage output version) or 21 ... 28 VDC (current
output version). When only the RS-485 output is used, 11 ... 28 VDC is
enough in typical measurement conditions.
When measuring in pressures 20 ... 50 bar
a
(290 ... 725 psi
a
) or
temperatures -40 ... 0 °C (-40 ... 32 °F), a supply voltage of 21 ... 28 VDC
is required.
The power supply should maintain the voltage for all load conditions.
The voltage fluctuations must be smaller than 0.3V, as continuous supply
voltage fluctuation may interfere with the auto-calibration function.
- If auto-calibration has failed due to the voltage fluctuation, you can
verify it using the STAT command on the serial line. See section
Show Transmitter Status on page 36.
- If auto-calibration fails repeatedly, the Autocal error code will be
activated. See section Error Codes on page 61.
Current consumption during normal operation is 20 mA. The
consumption increases during auto-calibration and sensor purge. The
maximum current consumption is 220 mA pulsed current.
NOTE The DMT152 can be powered by the MI70 indicator or the Vaisala USB
cable. However, the power supplied by these devices may not be enough
for all functions of the transmitter (for example, the current output).
If you are using a separate power supply in connector I, connect the
power supply first before connecting the USB cable or the MI70
indicator. The order is important, since the transmitter will use the power
supply that is connected first.