System 83 Ballistic Instrumentation

PRESSURE READINGS

The System 83 measures chamber pressure using a 0 – 10 volt signal from an external transducer and charge amplifier. This signal is digitized (10 bit accuracy) at 18 microsecond intervals. The pressure curve is displayed on the computer screen immediately after a shot is fired, and digital readings are provided for peak pressure, area under pressure-time curve, and rise-time. The displayed pressure curve can be chosen to be either 2 or 4 milliseconds in duration. Curves are stored for subsequent printout.

Alternatively, the System 83 can measure chamber pressure using a small strain gage glued over the chamber area of a barrel. The dimensions of the barrel and the assumed material characteristics provide the scale for the pressure measurements.

VELOCITY READINGS

The system uses either two or three Model 57 Infrared Photoelectric Screens located near the muzzle. If used, the third screen is located at the midpoint between the other two. The system displays instrumental velocity between the two primary screens. The proof channel displays the difference in velocity measure between first and middle screens referenced to the velocity measured between first and last screens.

The system can handle three additional Model 57 Infrared Photoelectric Screens downrange to measure terminal velocity, time-of-flight, and ballistic coefficient. The 8355 downrange adapter is required to use the additional M-57 screens downrange.

ACOUSTIC TARGET

The ACOUSTIC TARGET may be used for bullets with a remaining velocity of greater than 1500 fps at the target. Four acoustic sensors record the passage of the bullet’s Mach cone. The system displays the exact hit location on the target, time-of-flight, ballistic coefficient, and estimated velocity at the target.

MACHINE GUN RATE-OF-FIRE

The System 83 measures the rate-of-fire and the velocity of individual rounds in burst fire. It can capture the data from each round of a 30-round burst, at up to 2,000 shots-per-minute.

SYSTEM 83 UNIT

The metal case is 17″ wide x 8″ deep x 1.75″ high, and can be fitted with ears for mounting in a standard 19″ rack. The System 83 must be connected to a Windows® computer via an RS-232 serial port.

HOST COMPUTER

The computer furnished by the user must be capable of running Windows® 95 or later operating system. The computer must have a serial port to connect to the Model 83. If the computer has no built-in serial port, the user must provide a converter that adapts an USB port to RS-232.

SOFTWARE

Model 83 32-bit software for Windows® 95, Windows® 98, Windows® ME or Windows® NT, Windows® 2000, and Windows® XP is now available. Evaluation versions can be obtained from Oehler Research for current Model 83 owners. The Windows® version of the Model 83’s program adds some of the most asked for features while retaining the general functionality of the Model 83 DOS program.

The Windows features include:

• Windows printers are supported and there is a print preview option so you can see reports before you prints them.
• Color printing is supported, and you can add your own company title to the top of printed reports.
• We added a multi-test summary report which combines shots from two or more groups into a large sample and then calculates the statistics of the combined group.
• We added the following fields to the test set up display: Operator, Test Bay, PC/Press (Picocoulombs per PSI), Vel Correction, Press Correction, Max Avg Press, and Avg Velocity.
• The test directory gives you several ways to sort tests or select tests that use a particular gun or load. The directory also shows the number of shots in a group, date, what’s measured, gun name, load name, operator, and test bay. The new directory makes it much easier to find the test you want.
• You can now measure pressure only requiring input from muzzle screens.
• You can select to use either two or three muzzle/downrange screens.
• The target now shows bullet holes to scale, the displayed and printed views of the acoustic target groups look more like the physical target.
• Communications between the PC and the M83 is more robust. Even if the M83 is shut off accidentally during a test, it can be reinitialized and the remaining shots in the group can be measured and included in the existing group.
• Diagnostic information is improved and raw time data can be displayed for any shot.
• You can add notes anytime during a test or when a test is replayed.
• The program supports longer test, gun and load record names, and long file names are supported for test, gun, and load files.
• Test data can be exported to Ballistic Explorer version 5.x and as a standard xBase database file.
• Individual tests can be copied from one test file to another test file. This feature helps you organize your data for future use.
• The DOS program’s tests can be imported into the new program. Gun and load data from one or more DOS test files can be added to the new program’s gun and load files.
• A full metric version of the program is available.

TEST RESULTS

The sample output page shows the complete test results. A complete record of the test conditions is shown in the left column of the upper block. Complete gun and transducer information is shown in the center column. Complete load information is shown in the right column. All individual results (velocities, time-of-flight to target, ballistic coefficient, pressure data and pressure curve) are shown for each shot. A summary block includes the statistical summary of each parameter, and a target plot shows the recorded group along with group measurements. The summary is followed by a condensed standard-atmosphere ballistic table computed from the measured velocities and ballistic coefficients.