Chapter 8 Tutorial

Relay Life and Preventative Maintenance

Relay Life

As a relay is used, the contacts begin to wear and the resistance of the closed contacts increases. The initial contact resistance of a relay is typically 50 mΩ (plus lead resistance). When the contact resistance exceeds 20 to 50 times its initial value, the contact resistance becomes very erratic and the relay should probably be replaced. For most applications, a relay with contact resistance greater than 1Ω should be replaced. The graph below shows the typical contact resistance characteristics of the relays used on the 34970A switching modules.

Relay Contact Resistance

Typical Relay Lifetime

Full Load Typical Signals No Load

1Ω

0Ω

1k

10k

100k

1M

10M

100M

Relay Operations (Cycles)

Relay Load

For most applications, the load switched by the relay is the most important factor affecting relay life. As shown in the graph below, relay life is maximized by switching low power. As the power switched increases, relay life deteriorates.

Voltage Switched

300V

Maximum Switching Capacity

240V

 

180V

120V

60V

0.2A

0.4A

0.6A

0.8A

1A

 

 

Armature (34901A, 34903A, 34904A, 34908A)

 

 

 

 

 

 

 

 

 

10 mA

20 mA

30 mA

40 mA

50 mA

 

Reed (34902A)

 

 

 

 

 

 

 

 

 

Current Switched

400

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Agilent Technologies 34970A manual Relay Life, Relay Load
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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.
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