Chapter 8 Tutorial

Actuators and General-Purpose Switching

The maximum value for Rp is usually made equal to the load resistance RL. Therefore, the limits on Rp can be stated as:

V

Imax < Rp < RL

Note that the actual value of the current (Io) in a circuit is determined by the equation:

V

Io = R L

Where V is the peak value of the source voltage and RL is the resistance of the load. The value for Io will be used to determine the value of the protection capacitor (Cp).

In determining the value of the protection network capacitor (Cp), there are several things that you will need to consider. First, the total circuit capacitance (Ctot) must be such that the peak voltage across the open relay contacts does not exceed 300 Vrms. The equation for determining the minimum allowable circuit capacitance is:

Ctot (Io / 300)2 x L

where L is the inductance of the load and Io is the current value calculated earlier.

The total circuit capacitance (C) is actually made up of the wiring capacitance plus the value of the protection network capacitor Cp. Therefore, the minimum value for Cp should be the value obtained for the total circuit capacitance (C). Note that the actual value used for Cp should be substantially greater than the value calculated for C.

Using Varistors

Use a varistor to add an absolute voltage limit across the relay contacts. Varistors are available for a wide range of voltage and clamp energy ratings. Once the circuit reaches the voltage rating of the varistor, the varistor’s resistance declines rapidly. A varistor can supplement an RC network and is especially useful when the required capacitance (Cp) is too large.

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Agilent Technologies 34970A manual Using Varistors

34970A specifications

Agilent Technologies 34970A is a versatile data acquisition and measurement system that has gained popularity in various industries, including research and development, manufacturing, and education. The primary purpose of the 34970A is to offer an efficient solution for data collection, monitoring, and analysis, which can significantly enhance productivity and accuracy in testing applications.

One of the main features of the 34970A is its modular design, allowing users to customize the system according to their specific measurement needs. The mainframe can accommodate up to three plug-in measurement modules, which can include various types of measurements such as analog, digital, temperature, and frequency. This modularity provides flexibility for users to tailor the system to their requirements, making it highly adaptable to different applications.

Another notable characteristic of the Agilent 34970A is its impressive channel configuration. The system can support up to 120 measurement channels when fully configured, enabling extensive data acquisition without the need for multiple devices. This capability is essential for applications requiring simultaneous monitoring of multiple parameters or locations.

The 34970A utilizes advanced signal processing technologies to ensure high-accuracy measurements. The internal 6.5-digit resolution multimeter provides precise readings, while the device also supports various input types, such as thermocouples and RTDs for temperature measurements. The ability to perform mathematical functions, such as summation and averaging, on the acquired data further enhances its usability.

For data storage and management, the Agilent 34970A features built-in memory for storing up to 20,000 readings. Users can also easily transfer data to a PC through the RS-232 interface or GPIB (IEEE 488) for further analysis and reporting. Additionally, it offers the capability to program automatic data logging and scheduling of measurements, which streamlines the testing process and reduces manual intervention.

In terms of user interface, the 34970A is equipped with a large graphical display that provides clear visualization of measurement data and easy navigation through settings and options. The menu-driven interface makes it accessible for users of all skill levels, simplifying the setup and operation of the device.

Overall, the Agilent Technologies 34970A stands out for its modularity, high channel capacity, advanced measurement technologies, and user-friendly interface. As a reliable and efficient data acquisition system, it is well-suited for a wide range of applications, making it an essential tool for engineers and technicians looking to enhance measurement precision and efficiency.