Seismic Seismic Source Wireless Radio Trigger Link

The Wireless Trigger Box 4 (WTB4) system is designed to operate with any seismograph and any mechanical impact source. There are two parts to the WTB4 system:

• One WTB4, the “Source” WTB4, senses the trigger pulse from the hammer switch, calculates its true GPS T0 time and transmits it to the “Recorder”.

• The second WTB4, the “Recorder” WTB4, receives the GPS time of the trigger signal from the “Source” unit and starts the seismograph.

Each WTB4 unit consists of:

• Internal Radio Trigger Module (RTM)

• Internal 4 watt VHF radio

• Internal 99 watt-hour rechargeable battery

• Internal GPS module

• All in sturdy composite/aluminum enclosure

The Source WTB4 sender unit is designed to operate with multiple Recorder WTB4 units.

RANGE: When both the receiver and transmitter are on ground level with a clear line of sight, the max range is estimated to be between 650ft and 950ft. With both units elevated a few feet above ground level, the estimated range is up to 1,600ft. Weather conditions and line of sight greatly affect the maximum range of the WTB4 units. Terrain, vegetation, structures and other obstacles obstructing the line of sight between the transmitter and receiver will negatively impact the maximum range. Excess moisture/rain will also cause a negative impact on the maximum range. 

Features and Benefits: Precision - Unlike standard trigger systems, the WTB4 uses GPS-based time codes to relay precise trigger times to the seismograph. Robustness - Using digital timing removes the errors introduced by transmitting analog tones over the voice channel of an analog radio. Flexibility - The VHF radio featured in the WTB4 both removes the burden of moving the trigger line between shots, and increases the range and overall usability of the system. Reliability - The WTB4 unit is the newest member of the Seismic Source line of data acquisition equipment. It is based on the DX-6 and U•Node 2 design, which will be the new standard for seismic electronics.

Theory of Operation:

All Wireless Trigger Box 4 (the WTB4) units, whether connected to a source or seismograph, must have a valid GPS lock. The Source WTB4, connected to the source with a hammer switch or other device, senses the time break. The WTB4 calculates the GPS time of the event, then transmits it to the Recorder WTB4 units via VHF radio.

The Recorder WTB4 units, the ones connected to the trigger port of each seismograph, receive the trigger time. They add one second to the received event time, and then trigger the seismograph accordingly. These seismographs, which must have a one second pre-trigger time programmed into them, start storing data once they receive the trigger signal from the attached WTB4.