如何为测量选择正确的脉冲类型

您是否曾经在P（Pulse）数据记录器终端上进行过传感器工作，但在C（控制）端子上没有使用传感器？是选择的列表PConfig参数PulseCount()指示艰巨？坎贝尔科学数据记录仪提供了几种测量脉冲信号的选项。我们的捷径Program Generatorwill select the right option for you in the case of directly supported sensors. For other sensors, you must determine the correct option to choose in the parameter available in eitherPulseCount()在CRBASIC或通用脉冲传感器中以捷径为单位。必须为脉冲端子选择正确的选项以正确测量信号。

This article will explain the differences in the options, so the next time you connect a pulse sensor, it should be simple. Beware that this article’s information will get a bit technical, but it will get directly to the point.

Matching Sensor Pulse Types with Data Logger Terminals

这re are three main types of pulses:

• 高频
• 开关闭合
• Low-level AC

检查传感器的文档，以便您知道其具有哪种输出类型。这CR6 Dataloggerhas U terminals that can be configured for any pulse type. Other data logger models have terminals dedicated for different types of pulses. Your data logger specification sheet will indicate which terminals can measure the pulse type you are interested in.

高频（或方波）

通常被称为高频脉冲方波。这voltage on the line quickly rises to a set value, such as 5 V. The voltage remains high for a set amount of time then quickly falls to a neutral value, usually ground. The voltage pulses look roughly rectangular, like a series of square- or rectangular-shaped waves. A large variety of sensors have this type of output.

测量高频脉冲的端子通常使用下拉电阻。下拉电阻确保脉冲之间存在清洁0 V，从而提供对电噪声的阻力。C坎贝尔科学数据记录仪上的C端子具有内部100 KOHM下拉电阻。根据您拥有的数据记录器模型，其他终端类型也可能能够读取此类脉冲。

Switch Closure

Switch-closure outputs do not actively drive a pulse. A switch closure is simply a mechanical switch to complete a circuit. Rain gages typically have a switch-closure output. Some flow meters and anemometers also use this type of output.

开关关闭时，在一根电线上施加的电压使脉冲出现在另一根电线上。需要用上拉电阻将电源放在电路中。上拉电阻为电路提供动力，同时限制电流以保护开关。设置为切换模式的P端子使用内部上拉电阻。您通常可以通过添加外部上拉电阻来使用其他端子。如果您需要测量比P终端更多的开关闭合，请参阅数据记录手册。

因为开关是机械的，所以实际的金属触点猛击关闭时会反弹。弹跳在脉冲开始时会产生一系列快速的尖峰。信号必须“拒绝”，以使尖峰不计为单独的脉冲。通过RC电路或软件计时进行汇总过滤。

Low-level AC

低水平的交流脉冲是在正电压和负电压之间摆动的信号。波形看起来是正弦的。这种类型的脉冲通常被视为许多动态计的输出。读取低级交流信号需要特殊电路。P终端CR1000 dataloggerand the even-numbered U terminals on theCR6 Datalogger具有直接连接所需的电路。这CR300，，，，CR310，和CR200X系列数据Alogger具有专用的P_LL终端。您可以使用LLAC4moduleto convert low-level AC signals to square-wave pulses when you need to connect additional anemometers.

其他脉冲类型

除了三种主要类型的脉冲外，还有其他一些变化需要注意。

打开收藏家

打开的收集器和开放排水脉冲型输出是使用固态开关代替机械开关的开关盘输出。由于开关不是机械的，因此不需要召唤过滤。开放式收集器和开放排水管可以成功地将其视为开关关闭脉冲。如果频率超过开关闭合的极限，则可以将其读取为带有上拉电阻器的高频脉冲。

Period Average Measurements

一个周期平均测量值测量收到一定数量的脉冲所需的时间。而不是一个PulseCount()instruction, which measures continuously, a period average measurement is done over a short timeframe. On Campbell Scientific data loggers, period average measurements are performed on analog input terminals.

为你推荐：If you need to perform a period average measurement, refer to the CRBasic Editor Help file for theexecravg()instruction. To access the file, highlightexecravgin the instruction list, and click theHelpbutton above the list. For assistance with accessing the CRBasic Editor Help file for a particular instruction, watch the“ CRBASIC |帮助系统”视频。

Conclusion

Campbell Scientific data loggers are capable of measuring all the main types of pulses. Measuring the signal successfully is a matter of selecting the proper terminal for the connection and the proper option for thePulseCount()数据记录程序程序中的说明。如果您曾经遇到过本文未涵盖的脉冲输出类型，请在下面发表评论。