Low error, switchable measurement lead detect circuit,申请号US19990264607-传众专利搜索

Low error, switchable measurement lead detect circuit

申请公布号：US6281673(B1)

申请号：US19990264607

申请日期：1999.03.09

申请公布日期：2001.08.28

申请人：

FLUKE CORPORATION

发明人：ZOELLICK RAYMOND D.;MILLER DOUGLAS A.

分类号：G01R15/12;G01R19/00;(IPC1-7):G01R19/14

主分类号：G01R15/12

摘要：A low error, switchable measurement lead detect circuit (9) for providing accurate current measurement readings and reducing susceptibility to false measurement lead detections due to leakage current is described. A gate (14) that receives an input select voltage Vs selectively connects either a supply voltage, Vd, or ground to the input of a voltage divider (13). Vd is connected during a measurement lead detection mode of operation or open fuse detection mode of operation, and a ground is connected during a current measurement mode of operation. During the measurement lead detection mode of operation, if the pin of a measurement lead is present in a split jack (12), the voltage divider (13) divides the supply voltage, Vd. Conversely, if no measurement lead pin is present in the split jack (12), the output voltage, Vo, of voltage divider (13) equals the level of Vd. During open fuse detection mode of operation, a measurement lead is present in the split jack (12), and if a fuse (F1) is present, the voltage divider divides the supply voltage, Vd. If a fuse (F1) is not present or is blown, the output voltage, Vo, of voltage divider (13) equals the level of Vd. During the current measurement mode of operation, the voltage divider (13) and shunt (11) form a series parallel circuit when a measurement lead pin is located in the split jack (12). The impedance of the shunt (11) is negligible in comparison to the impedance of the voltage divider (13), and the voltage drop across shunt (11) is proportional to the injected current. Because the voltage divider (13) is grounded through the gate (14) during the current measurement mode of operation, no error current from supply voltage, Vd, passes through the shunt (11). As a result, the accuracy of current measurement readings made during the current measurement mode of operation is improved. Because the supply voltage does not produce an error current during the measurement mode of operation, the overall impedance of the voltage divider (13) can be reduced to reduce susceptibility to leakage current during the measurement lead detection mode of operation.