Hydrological Services Pty Ltd
Data Logger Model ML1-420
©
Copyright
ML1-420 100-28
Issue 1.00 6 Apr, 2011
5.2
LED Indicator
The LED indicator on the MiniLog ML1-420 will flash once a second. This heartbeat
indicates that the MiniLog is alive and well. (Note that the flash is only 1 mS in duration and
has an insignificant contribution to the battery life.)
When an external event or communication occurs, the LED flashes much longer. This makes
it easy to distinguish an event from the heartbeat. When a 4-20mA sample is in progress the
LED flashes at a 5Hz rate.
5.3
External Contact Interface
The MiniLog ML1-420 logger includes an interface for an external voltage free contact. The
occurrence of an external event causes the logger to wake momentarily, record the event to
the historical record, transmit the event on the serial port (if the EV flag is on), update the
Total Events and Events Today before going back to sleep.
5.4 4-20mA
Interface
The MiniLog ML1-420 logger has a 42.9 ohm sense resistor for measuring the 4-20mA
current, as well as the ability to switch loop power to the 4-20mA device. The measurement
cycle causes the logger to wake, switch power to the 4-20mA transducer, wait the required
warm up time, make a measurement, record the measurement to the historical record, transmit
the measurement on the serial port (if the EV flag is on) before going back to sleep.
5.5 Communications
Interface
The communications allows for simple direct connection to a PC. The hardware interface is
standard RS232, and the low consumption of the MiniLog means that sufficient power can be
extracted from the RS232 handshake lines to power the logger while a communication
session is in progress. Seven baud rates can be selected.
5.6 Watchdog
The MiniLog incorporates ‘watchdog’ circuitry within the microprocessor to automatically
recover from unforeseen software or noise induced failures. The action of a watchdog reset
does not affect previously recorded data or any set-up parameters including date and time.
5.7 Power
Supply
The MiniLog is powered by an internal AA battery, for normal event logging. This can be
anything from a NiMH (1.2V) to an alkaline (1.5V) to a lithium (3.0V or 3.6V) – with each
type of battery giving a different life. External power is required during a communication
session – but this is normally provided through the RS232 handshake lines when an RS232
cable is connected.
External power is required if a 4-20mA transducer is connected - use 6V DC to 19V DC.
