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The Stalagmate Plus Mk2b is a self-contained battery-powered box slightly larger than a 5cm cube which records stalactite drop discharge rates for up to four years.

The box is fitted with a data port sealed with a waterproof cap, electrodes for remote triggering and three LED's which indicate operating functions. The lid can be removed for battery replacement (see below) but care is needed when refitting the lid to ensure watertight integrity.

The Drop Sensor

The principle of operation is very simple: the lid is essentially a microphone which is "pinged" each time it receives an impulse from a falling drop. This damped oscillatory response is processed and converted into a clean rectangular pulse which drives a logger/counter on a separate PCB.

Each time a pulse is received, this is signalled by a brief flash from the yellow led on the side of the box. The sensor rejects ambient noise (voices, cascading water etc) which might produce a spurious response.

The Data Logger

The datalogger board is a proprietary product of Gemini Data Loggers Ltd and is programmable using Gemini's Explorer software for Windows XP or Vista. Power for the detector board comes from the logger battery so that it draws current only when the logger is activated after "Launch".

Since the logger draws only a few microamps when in "sleep mode", battery life is preserved for up to 10 years. In "run" mode battery life is up to 4 years.Logger capacity is 32,767 "buckets" each of which can be filled with 16,383 drip events.

Theinterval allowed for each bucket to fill is programmable from 1 second upwards, so that, for example, a 30 minute interval will allow the logger to run for 1 year and 10 months. The maximum recordable drip rate is 5 per second.

Data Communication

Communication with a PC is via a USB cable with a miniature 3-pin connection to the Stalagmate box. Data may be recovered using a laptop or netbook running Gemini Explorer (requires Windows XP, 2000 or ME) and exported as .csv file format.

Data may also be downloaded onto a PDA running Windows Mobile 5 using a free software patch available on beta release from