The correct answer is: D. All of the above
Programmable controllers (PLCs) are digital computers that are used to control industrial processes. They are more powerful than the first controllers on the market, and they are relatively low cost compared with the original digital equipment available for industrial control. PLCs can be cost effective even when replacing just a few relays.
Here is a brief explanation of each option:
- A. are more powerful then the first controllers on the market
The first PLCs were introduced in the 1970s, and they were relatively simple devices. They could only perform a few basic tasks, such as controlling motors and valves. Today’s PLCs are much more powerful, and they can perform complex tasks such as monitoring and controlling multiple processes.
- B. are relatively low cost compared with the original digital equipment available for industrial control
The original digital equipment available for industrial control was very expensive. PLCs were developed to provide a more affordable alternative. Today, PLCs are even more affordable than they were in the past, and they are a cost-effective solution for many industrial control applications.
- C. can be cost effective even when replacing just a few relays
In some cases, it may be more cost effective to replace a few relays with a PLC than to continue to maintain the relays. PLCs are more reliable than relays, and they can be programmed to perform more complex tasks. Additionally, PLCs can be easily monitored and controlled, which can save time and money.
In conclusion, PLCs are more powerful, more affordable, and more reliable than the original digital equipment available for industrial control. They can be cost effective even when replacing just a few relays.