PURPOSE:To reduce inaccuracy of judgement on test results faking place at the time of the contact inferiority of a probe. CONSTITUTION:An open device is provided with a means 42 which prepares criterions by using a good quality printed-circuit board 28, and when the measured resistance at a specified position on the said board exceeds the value inputted, the inputted value is decided as the primary criterion value, and when the measured resistance by the maximum range of resistance measurement at the same position exceeds the maximum range value, the secondary criterion is set up as the over-range, and, in the case where the measured resistance is less than the maximum range value the secondary criterion is set up as being in the range over the primary criterion value. Moreover, the device is provided with an open test means 48 for a printed- circuit board 28 to be tested, and judges whether the measured resistance value at the same position on the printed-circuit board 28 to be tested is over the primary criterion value or not. Hence it is judged whether the specified position is in a short circuit condition or not. When the measured resistance exceeds the maximum range value, the same position is measures again with the maximum range. And in the case where the measured resistance is over the maximum range value, a second criterion judging means 46 decides that the measured resistance is in the over range, and while in the case where the measured resistance is less than the maximum range, the secondary criterion whether the measured resistance is in the range over the primary criterion value or not. Hence the device can judge whether a probe is in contact inferiority or not.
展开▼
