CC-PAIH51 51410069-275 The complete test system has a total of n unit measurement circuits, which can realise multi-channel measurement of sensors. Each unit measurement circuit is designed in a four-wire system, and this four-wire structure requires a precision constant-current source; in addition, due to the weak output signal of the unit measurement circuit, it is also necessary to amplify the output signal for DC amplification, and then carry out A/D conversion after amplification.

CC-PAIH51 51410069-275 In order to improve the measurement accuracy and reduce the error brought by the peripheral circuit during measurement, this design adopts a multi-channel electronic switch Ka, which makes the n-channel unit measurement circuits share a precision constant-current source of 0.5mA, and at the same time, makes the n-channel unit measurement circuits share a common amplification circuit, i.e., in the measurement of Pt temperature sensors, it is possible to use a constant-current source of 0.5mA only when the electronic switch groups Ka and Kb group of the nth switch at the same time on the nth Pt temperature sensor can be selected and its parameters are measured.

The CC-PAIH51 51410069-275 uses 32 eight-selective multi-switching devices CD4051 and two 74LS138 to form an electronic switching array, which realises the control of 128 channels and allows the selection of any of the 128 Pt resistors for testing. Measurement circuit measured by the Pt resistance sensor voltage at both ends of the amplifier circuit into the MSP430 microcontroller for A/D conversion.