A frequency might come from a temperature sensor (MAX6577), an event from a Geiger counter or micro-switch, an On/Off signal from a voltage or boom switch.  In addition you may need to collect RS232 data from a device such as the Geonics EM38 soil conductivity sensor. (contact us for supported devices).

When only a few variables need to be logged and GPS located, you need  a system with  minimal cost.  Such a system can use the available pins of the Serial ports of low cost Windows CE/95/98/NT computers to record up to four data channels along with the GPS location. (Typical Wiring Diagrams.)

HGIS PROFESSIONAL Logs up to 9 channels as follows:
• GPS location data (1 dedicated channel)
• RS232 data (up to 8 dedicated channels)

• Frequency (up to 12 dedicated channels), or
• Events (up to 12 channels), or
• On/Off Switches (up to 12 channels)

The number of RS232 sensors is limited by the number of RS232 ports on the computer.  The ports must be numbered between COM1 and COM9.  (COM10 and above is not supported.)

The 232BSS4 four port RS232 Multiplexer can be connected to the computer through an existing Serial Port (usually COM1).  The multiplexer Port A is used for the GPS, and Ports B, C, and D are available for RS232 Geophysical Sensors. The Multiplexer ports do not support Frequency, Events, or Switches.

USB to Serial Multiplexers (EdgePort) may also be used (NOT on PocketPC computers) to add up to eight Serial ports to any computer that uses a "Master" USB controller (such as Laptops).  Pocket PC computers use a "Slave" USB controller and are therefore not supported.  The Multiplexer ports do not support Frequency, Events, or Switches.

With the Trimble AgGPS132, you can use the second serial port on the GPS for some Geophysical sensors.  The setup is a bit tricky on the AgGPS132, but if your sensor is supported, it is an extra serial port  (the extra Trimble data cable costs more than a plug-in Serial card, though). This port does not support Frequency, Events, or Switches.

Plug-in Serial cards are available in 1, 2, and 4 port configurations.  Frequency, Events, and Switches are supported with these Serial Cards.

Conclusion: when using Laptops, add a USB-Serial Multiplexer (up to eight ports).  With Pocket PCs, add either a 2-port Serial Card giving a total of 3 Serial Ports, or a 232BSS4 Multiplexer giving a total of 4 Serial Ports.

The frequeny/event/on-off inputs use the extra pins on RS232 port. This works with full implementations of RS232 only.  COM1 on many Pocket PC computers are only partial RS232 implementations.  The frequency limit is in the range of 1 kilohertz for Windows 95/98/NT and about 500 hertz for most Pocket PCs.   The frequency precision can be up to five significant digits for Windows NT; four significant digits for Windows 98, ME, and XP; Three to four digits on PocketPC and Windows CE.

The greatest advantage of frequency measurement using HGIS is that HGIS can accurately measure frequencies from 2Hz - 100Hz at up to three significant figures every second.  For example a shaft is rotating at 5.68 revolutions per second. HGIS can accurately measure the rotation EVERY SECOND to three significant figures.  Other systems might only report 5 or 6 revolutions per second (one significant figure).

The computer automatically logs in several formats.  You can log directly in a text file format that can be imported into spreadsheets and databases.  Or you can create maps with sensor data automatically attached to Point Objects in a Map Layer. When creating maps of Sensor data, you can only create points at one point (per port) per second.  However, when logging TXT log files, data may be logged at any rate supported by the computer; often 50-100 records per second (total of all ports).

SensorTrack does not record actual voltage(e.g. 4.52 volts).  It can record the presence of voltage (for example, an on/off switch connected to a battery).  To record actual voltage (or current or resistance),  use a Radio Shack  22-805 Digital Multimeter which has a Serial Output.