    
The Model 850 orientation sensor is designed to enable high accuracy measurement of the
toolface (roll), inclination and azimuth orientation angles in borehole logging and drilling
applications. Because of its small size, it is particularly well suited for use with coiled
tubing drilling and completion systems.
There are two submodels of the 850 system designated by the product numbers 850 and 850WL. The 850WL system is designed to be used with a wireline and has an internal modem to enable communication of the data output over a single conductor (plus ground) wireline. In all other aspects, the 850 and 850WL are identical. Both the 850 and 850WL systems power from single input voltage ranging from +12V to +30V.
The 850WL sensor is also available shock mounted in a 1.375" OD x 23½" long beryllium copper
pressure barrel (Model 850PB). This system is designed for wireline use and is
mechanically compatible with standard 1.375 OD oilfield running gear.
The Model 850 system contains both a 3 axis fluxgate magnetometer and a 3-axis
accelerometer. The combination of these two sensor systems enables the roll, inclination and
azimuth angles of the 850 sensor to be determined. To maintain high accuracy over the
temperature range of the system, the sensors are temperature compensated. This enables an
accuracy of ±0.1° for inclination and toolface and an accuracy of ±0.3° for azimuth to be
achieved over the full temperature range of the system.
The Model 850 is capable of transmitting the instrument temperature and either the magnetometer and accelerometer
outputs or the system orientation angles. The maximum transmission rate is 8 times per second
for magnetometer and accelerometer outputs and 4 times per second for orientation angles.
The Model 850 communicates with the outside world over a serial bidirectional TTL
interface. The serial in and serial out lines operate at TTL/CMOS levels and are normally set
to operate at 9600 baud with one stop bit and no parity. The user however can change the baud
rate by setting bits in the system EEROM.
Two communication protocols are available: 1) ASCII and 2) BINARY. The ASCII protocol is
based upon sending ASCII characters to the 850 to obtain data. The data returned by the
Model 850 is transmitted as an ASCII data stream complete with carriage returns and
line feeds so that it can be easily displayed on a video terminal (provided a TTL to RS232
conversion is made by the user). The binary protocol is used for high speed computer to
computer interchange. In this case, one byte is sent to request data. The Model 850
then responds with a multibyte data packet containing the desired data plus header and checksum.
The Model 850 can also be configured to continuously send data in ASCII or binary
protocol upon power up.
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