LogDator™

Low-power small form-factor environmental data logger

For custom environmental monitoring applications - real time or stand alone

The LogDator™ is designed for data collection and control of the SediMeter, but it can also be used separately (Item LD-02-00) with other sensors. Its small form factor and low power consumption makes it ideal for underwater use. It can return data immediately on a serial communication line, save data to internal memory, or save data to file on a memory card.

There are 2 A/D ports where OP-AMPs can be used for signal processing before the A/D converter. In other words, there are two channels for optional analog sensors, and they can be made to measure resistance, voltage, or current. These can be sampled up to 84 times per measurement, with a user-selectable frequency. Wave periods can be estimated from these data. Each measurement is the sum of 16 discrete measurements by the 12-bit A/D converter, an anti-aliasing method that results in 16-bit values. By taking 84 such samples very precise averages can be calculated, even from sensors with large random variations, e.g., pressure sensors.

Optional sensors that have been interfaced to the LogDator™ include: light sensor, pressure sensor for water depth up to 24 m, pressure sensor for measuring evaporation in a 10 inch deep standard evaporation tank, and a sensor for relative humidity in a meteorological measurement station.

The user interface consists of the NavPin control stick, with four directions plus select, together with a small display. This can be used to set date and time, start time, measurement interval, mode, etc. There is also a magnetic switch, which can be operated without opening the instrument, even under water. It is used to change mode, so that the instrument can be set up in advance, left in Sleep mode, and switched to Log mode when it is deployed. Similarly, logging can be turned off when it is retrieved, while waiting for it to dry sufficiently to open it.

The LogDator™ works with the SediMeter computer software for setup, download, data analysis, and real-time monitoring of a network of hundreds of LogDators or SediMeters, in any combination. Furthermore, it can act as a web server so the monitoring can be supervised from the internet.

The LogDator is developed in house, and programmed in house. If required, custom code can be written. This makes the LogDator a very versatile logger for environmental studies under water. It can also be used on land, if protected from direct sunlight and within its temperature limits (0 ºC – 50 ºC; the LCD display is the limiting component).

The network can be operated in one of two methods: By having a central computer permanently connected, or by letting the LogDators store data internally and retrieve the data at regular intervals using a computer. A master or central logger is under development. It will be an RS-485 network master LogDator™ that can gather data from up to 255 LogDators or SediMeters to an MMC or SD card of up to 2 GB capacity. When that becomes available the central LogDator will replace the computer, and for retrieving data one will just have to change memory card.

LogDator™ LD-02-00 key features (complete specifications)