The -999.9 appears because power was lost to the interface at some time after the sensor was set up. When that happened, the sensor calibration information was lost on the interface. There are a couple ways to solve this problem.

(1) You can reset the DataMate program by pressing the [CLEAR] button on the calculator. This reloads the calibration information onto the interface, but it also resets the DataMate program, which resets the data collection parameters. If you do not want to lose the data collection parameters, use the second method.

(2) The second method only reloads the calibration and does not reset the DataMate program. To use this method, simply press the [GRAPH] button on the 73/82/83 or 86 calculator or the [<--] button in the 89 or 92 while on the main screen of DataMate.