Recording Baro and Temp Sensor Shipping weight is 2 lbs., includes pressure and temperature sensors, software, cables, connectors, instruction manual and battery, as shown. Requires a serial port connection (USB to serial port adaptors can be used for this.) $129.00   ...item# 1868

Sensor unit is 3.75 x 2.38 x 1.00 inches

This product, called a "Weather Jack," is a remote temperature and pressure sensor that can be read at any time by connecting it to a PC with a simple phone cord into a serial port connector for your computer. All connectors and cables are provided, as well as the 9v battery that runs it -- for a year or so. Temperature and pressure can be recorded at any interval, from 15 minutes on up. At 15-min intervals it will store 5 days of data; longer intervals store for longer periods. This is the same sensor used in the Jumbo Barometer, which is highly accurate and the offset is simple to set to get correct sea level pressure. The temperature sensor could be used for sea water temperature or air temp... we have had one sailor use it to monitor their fridge temp. Hikers can use it to record elevation changes during some outing, which they replay and plot when they get home. (Formulas and procedures for deriving elevation from pressure are in the Resources Library under Miscellaneous.) The data are stored in the PC as simple text files that can easily be imported into a spread sheet or data base for comparison with other measurements... as done below. These devices are ideal for detailed recording of the approach and passing of weather systems. A sample of a front passing over us in the Southern Straits of Georgia yacht race is shown below. The blue data are from a weather jack in a sail bag, the red data were provided to us by Environment Canada a few days after the race. For the first few hours, the sail bag with Weather Jack in it was not on the boat but at a higher elevation at the hotel, hence the early discrepancy with sea level pressures. Note that you can even see 1-hour trends being reproduced in the measured data. This graph is a direct output from an Excel spreadsheet plot. Our measurements show that the relative and reproducible accuracy of the device is < 1mb, with +/- 0.5 mb as typical. This means that if you set the device to to a proper accurate pressue, all subsequent pressures read from the device will be accurate to within about +/- 0.5 mb. Below is a screen shot of the software interface to the device from the PC. Or you can customize the interface and not use the software that comes with it. The data are stored in a simple text file that can be imported into Excel and your own graphic display created. The sensor can be interrogated with Hyper Terminal to update the data log in the PC and extract data. Using this method you can also change the sample times to any interval you choose, whereas the packaged software limits sample intervals to 15m, 30m, or 1 hr. Regardless of how it is set, a total of 127 measurements can be stored. At 1 hr intervals, you have some 5 days of data; at 1 min intervals you store about 2hr of data. After the 127 points have been filled, it will start to overwrite the earliest ones with new data. The temperature sensor: You can attach the sensor to a pole and the pole to a stanchion so as to measure the water temperature underway. This is extremely valuable sailing in the Gulf Stream for noting your location within main streams and meanders, and it is also valuable sailing in the tropics since waters above 80°F could be breeding grounds for tropical storms, and cooler waters are not. The sensor is accurate to ±1°F. View Weather Jack Barometer manual (250kb pdf) Compare electronic barometers we offer Compare devices similar to Weather Jack There are not many devices of this type available in this price range, as far as we can tell—that is, a pressure sensor designed to be controlled and read by your computer. Here are the ones we have found so far: http://www.fischer-barometer.de/english/index.htm (from this link, select "Barometer, electronic" in the top left drop down.) http://www.vaisala.com/businessareas/instruments/products/barometricpressure http://www.control3.com/1870p.htm (sensor) and http://www.control3.com/4136p.htm (software) There are also several references to one called "Prosser Weathertrend digital barometer," which can be read by a PC or from a simple dial, but we cannot locate where to buy it. It appears to be from UK. There may also be more options if you consider a full remote weather station, as opposed to just pressure and temperature, but they would cost more (ie http://www.robertwhite.com/cgi-local/shop.pl?type=item&item=wm-da-weathermonitor&categ=rw_digital_weather_stations&nav_bar=weather -- sensor and software sold separately)... also to be competitive with the Weather Jack we should be able to program the time interval that it samples the pressure and be able to change the scale constant so it can be set to any elevation.