使用 SN8P1702A 的低成本上下限通用数字表头

图示电路是一款输入电压 DC200mV ,满度读数 2000 个字的数字电压表头电路.分辨力达到 100uV/字 .这种参数与通常使用的 3 位半数字表头相吻合,(但是这里没有负电压信号的测量功能).因此,可以方便地在无需负信号输入的场合替换原来的数字表头.

替换带来的好处是这里具有上下限设置的控制功能,而普通的 3 位半数字表头却只能测量显示而不能进行设置控制.

配原理图应用和连接说明:

图A:测量和控制直流 200mA 信号.如果是交流信号,需要先有 AC-DC 转换.

图B:测量和控制直流 200mV 信号.如果是交流信号,需要先有 AC-DC 转换

图C:测量和控制直流 4～20mA 信号.这种信号可以远传,例如压力传感器的输出.输入配置的 -50mV 电压是在输入 4mA 的时候,恰好抵消取样电阻上的压降而设.实际中需要使用低内阻的恒压源.

图D:测量和控制温度测量信号.LM35D 具有 10mV/℃ 的输出,因此,通过 10:1 的分压,达到 1mV/℃,100℃ 就是 100mV,100mV 就显示 1000 个字,把小数点定位在十位上,就是 100.0℃

附有 AD 转换部分的源程序-Use SN8P1702A low-cost universal digital meter on the lower

Icon is a circuit input voltage DC200mV, full-scale reading of 2000 characters digital voltage meter circuit. Resolution to 100uV/word. This argument often used three and a half number of the header match, (but there is no negative voltage signal measurement function). Thus, it can easily without a negative signal input the number of occasions replace the original header.

The benefits are here to replace a set of control functions on the lower limit, while the ordinary three half-meter can only measure the number of display and control can not be set.

Schematic connection with the application and instructions:

Figure A: 200mA DC measurement and control signals. If the AC signal, you need to have AC-DC conversion.

Figure B: 200mV dc measurement and control signals. If the AC signal, you need to have AC-DC converter

Figure C: measurement and control of DC 4 ~ 20mA signal. This signal can be remote, such as pressure s