Exit Consulting
is proud to offer the GPSClock 200

The GPSClock Model 200 is a clock that is accurate to a millionth of a second. It is not like the radio 'atomic' clocks that are accurate to half a second or so. For more details about how the clock works and what it is good for, read the FAQ.

We're now accepting orders for the GPSCLOCK 200; you may order one here. We accept American Express, Mastercard and Visa as well as personal and cashier's checks and money orders. We ship both domestically and internationally.

Features:

• Operates anywhere on the surface of the Earth
• Y2K compliant, GPS week rollover compliant
• Compact, weatherproof, easy to mount
• Wide supply voltage range, 8V-40V
• 1W typical power consumption
• PPS pulses accurate to plus or minus 1 microsecond of UTC
• Tunable to plus/minus 250 nanosecond accuracy
• Fifteen-meter (fifty-foot) cable included
• Turns off PPS output when not synchronized
• Designed specifically for timing applications
• Can be configured to delay/advance PPS pulse
• Can provide position data in WGS84, WGS72, NAD83, NAD27, and other formats
• Can maintain timing accuracy with only one satellite
• Includes web page builder, NTP patches and DOS support software
• Low cost ($380)
• Includes detailed manual

Specifications:

Weight:	Less than one pound, without cable
Size:	4.5 inch diameter, 3 inches high
Mounting:	Screws onto PVC pipe
Cable length:	15 meters (50 feet), can be extended
Positioning accuracy:	<100 feet
Timing accuracy:	Plus or minus 1 microsecond to UTC
Warranty:	90 days

The GPSClock 200 has an RS-232 output that provides NMEA time codes and a PPS output signal. About a half-second before, it outputs the time of the next PPS pulse in either GPRMC or GPZDA format. Within one microsecond of the beginning of the UTC second, it brings the PPS output high for about 500 ms.

It also supports GPGGA, GPGLL, GPGSA, GPGSV, and GPVTG messages at configurable intervals. It has 2D and 3D positioning modes and can maintain rated time accuracy even with only a single satellite in view.

If the position is within 90 miles of the last fix and the unit last had a fix within 4 hours, a first fix is typically available within 20 seconds of power application. If the last fix was less than a month ago and the unit has been moved less than 90 miles, typical time to first fix is 45 seconds. If the unit has had a fix less than a year ago (and the almanac has not been cleared), a fix can usually be made in 15 minutes.

You will have to provide your own power supply. Any wall transformer that can supply between 9V and 24V DC at 120mA will do. You will also need to wire your own connector onto the GPS clock and make a cable to connect it to your computer's serial port. Some simple soldering is required.

The only components you'll need to add are a DB9 connector, a power supply and LEDs and resistors if you want the optional power, data or lock indicators. A 15 meter (50 foot) cable with a weatherproof boot is included.

A minimal adaptor with no indicators is as simple as wiring your DC supply's positive output to the clock cable's red lead and negative output to the clock's black lead. Then you wire the clock's blue lead to pin 1 on a DB9 connector, the clock's white lead to pin 3, the green lead to pin 2 and the yellow lead to pin 5. Plug in the transformer and connect the DB9 to your serial port and that's it, you're done! You can fit the entire thing inside the DB9 connector housing. Here is picture of such a connector:

To the right is a picture of one keeping time on a shelf. This is not just the antenna -- the whole device, antenna, switching power supply, receiver and decoder are all inside that small round sealed enclosure. The round object in the foreground is a quarter, shown for scale. On the bottom is the coupler that allows you to screw it onto the end of a pole. You can also see the weatherproof boot around the cable connector. The GPSClock 200 sells for $380. Orders may be paid by American Express, Visa, Mastercard, money order or cashier's or personal check. Shipping time is one to six weeks, depending on stock availability. You may place your order at the Exit Consulting Store. See the FAQ for more information.

Operation within specifications is dependent upon proper mounting and access to open sky. Ideally, an outside pole mount should be used, giving the unit an unobstructed view of at least 70% of the sky above 10 degrees elevation. However, mounts far less than ideal will work.

Note that the PPS output must be used to get microsecond time accuracy. Your time would be offset by at least 400 milliseconds and accurate to no more than 25 milliseconds using just the serial output. This may be adequate for many applications, however.

If you'd like to see a GPS device in action, look at this live GPS view.

See a GPSClock's statistics.
Learn about using GPS for time Synchronization.