The new generation terraTEM, the terraTEM24, has been designed to acquire high‑quality transient electromagnetic data from a wide variety of sensors ranging from remote inductive and B field sensors through to single loop and coincident loop configurations.
The terraTEM24 is available as a 1, 2, 3, 6 or 9 data channel system. Data are simultaneously recorded from all channels. Purpose-built true 24 bit ADCs and dedicated signal paths for each channel ensure data integrity.
Channels have input voltage protection up to 700 V and have measurement range starting at +/- 200 V for coincident and single loop inputs, and +/- 20 V for active sensors. User-selectable internal gain stages allow for better resolution of low signal levels. This extends the system dynamic range to 198 dB. When combined with a user-selectable maximum sample rate of 625 kHz and the ability to be configured with or without a 6 kW internal transmitter (50 Amp, 120 V) the terraTEM24 is a highly versatile system suitable for all TEM configurations.
Many of the popular features of the terraTEM have been enhanced for inclusion within the terraTEM24. These include the easy to use operator-interface, an internal transmitter, and complete integration with other products within the terraTEM suite including the external terraTX-50 transmitter, surface TRC receiver coils, the VECTEM downhole induction probe and TR_B Field sensor. Another point to note is that each receiver port is equipped with separate power output and RS485 communications which provides even more flexibility for integration with third‑party sensors.
The user interface has been designed to allow field operators to readily acquire data without complicated menus. Operators can rapidly assess transient response curves and perform in-field quality control. If required, survey parameters can be downloaded to the terraTEM24 from the survey designer to ensure compliance. The software allows for a comprehensive suite of diagnostic system information to be displayed along with oscilloscope, time series and spectral analysis capabilities for quantitative assessment of ambient noise from the receiver. Software includes export capabilities, allowing data to be exported in all industry standard formats including AMIRA, USF, XYZ and ASCII.
The internal transmitter has undergone a radical remodelling with specifications increased to 50 A at 120 V, or 6 kW. The internal transmitter features an adjustable linear high-speed current turn-off, and the ability to record the full current waveform. The fast linear turn-off (36 microseconds at 50 A for a 50 m × 50 m loop) means that the high sampling rates of up to 625,000 samples per second per channel can be used for high resolution shallow target exploration. An optional 6 kW voltage rectifier, suitable for either single or three phase power input, gives the user flexibility to digitally control the transmitter current, maximising received signal without saturating early-time response. For those users who prefer the flexibility of a separate transmitter, the terraTEM24 can be configured as a receiver only, synchronising via cable, GPS or an optional crystal module to the external transmitter, the terraTX-50 (50 A, 250V). Options such as these are designed to give the user greater flexibility in survey design.
The increased input range of +/- 200 V is specifically tailored for coincident and single loop configurations and will reduce the early-time signal clipping, prevalent in many standard TEM systems. For active sensors the input range and therefore sample resolution is reduced using either the automatic or manual gain settings.
All terraTEM24 models are fitted with an internal GPS for accurate timing along with location information.
All of these features, combined with a 10”colour capacitive touchscreen, 30 GByte data storage and powerful software options, result in this new release terraTEM24 system setting the industry benchmark as did the terraTEM.