Instructions

UM-0085-B09 DT80 Range User Manual Page 290
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Other Considerations
The main battery is a "sealed" type; however it does contain a regulator valve on its top face near the terminals. This has
the following implications:
• Ventilation must be provided to allow any battery gases to escape. If the DT80 is mounted in a sealed enclosure
then a valve should be provided to prevent gas build-up.
• When operating at high temperatures, acid may seep from the regulator valve if it is facing downward. The
internal battery's terminals face the rear panel of the DT80. The logger should therefore be oriented either in
table top configuration (keypad/display facing up), or wall mounted (input terminals facing down). It should not
be wall mounted upside down (input terminals facing upwards) because then the battery terminals and regulator
valve would face downward.
Power Outputs
As shown in Figure 119 (Series 2 and 3) or Figure 120 (Series 4), the DT80 provides various general purpose power
outputs.
Standard Outputs
For the following power outputs the return terminal is DGND.
• The PWR OUT terminal (DT85 only) provides a current limited power output derived from the external power
input. The output voltage will be 1-2V below that of the external power input. If you attempt to draw more than
the rated maximum current then the voltage output will drop.
• The 12V terminal (series 3 logger or older) provides a switched regulated 12V output (max 150mA). Unlike
PWR OUT, this power is available even if the logger is running on battery power.
• The switchable 12V/ 5V terminal (series 4 logger) provides a switchable 12V or 5V with the current capabilities
up to 300mA. This terminal replace 12V terminal in series 3.
These power outputs may be used to power such devices as:
• CEM20 channel expansion modules (see The CEM20 (P375))
• relays (see DO1 – Driving a Relay (P335))
• SDI-12 sensor networks (see SDI-12 Channel (P342))
• modems (see also Powering the DT80’s Modem (P203))
• application-specific digital interfaces
Note: The plug pack supplied with the DT80 is rated at 15V 800mA (12W). However this may be insufficient for a DT85 with fully loaded
power outputs and a flat internal battery, in which case a higher capacity power supply may be required. See Power Consumption
(P292) for more details.
Isolated Output
The Series 3 models provide an isolated switched 5V output, 5V SW. The return terminal for this power output is AGND.
This output is typically used for powering analog sensors. Maximum output current is 25mA.
Controlling 12V Power Output
Series 2, 3 and 4
The switched 12V output may be controlled in three different ways:
• It may be switched on or off manually using the
PWR12V (or 1SSPWR) channel type. Use PWR12V=1 to switch
on the 12V output, or
PWR12V=0 to switch it off.
• It may be switched on automatically prior to execution of a schedule containing CEM20 channels. (As noted in
Powering the CEM20 (P377), any connected CEM20 units are normally powered using the 12V output.)
• It may be switched on or off automatically if the DT80 is configured to power a modem using this power output,
as described in Powering the DT80’s Modem (P203).
Controlling 12V/ 5V Power Output
Only Series 4
Addition to PWR12V syntax on the same 12V terminal on Series 4, it is possible to switch into 5V output using
PWR_OUT
syntax.
• Series 4 loggers offer two output levels: PWR_OUT=12 is used to trigger 12V output while PWR_OUT=5 is
used for providing 5V output. The return terminal for both 12V and 5V power outputs is DGND.