220-1101 Question 243
Single answerCommunications interfacesA field technician is connecting a legacy environmental sensor to a new desktop PC for data collection. The sensor's documentation specifies an RS-232 serial connection and uses a DB-9 connector. The new PC does not have a built-in serial port. The technician needs a solution that will allow the software to communicate reliably with the sensor without opening the PC case. Which of the following is the BEST option?
- A
Install a USB-to-serial adapter that presents a COM port to the operating system
- B
Use an HDMI-to-VGA adapter to connect the sensor to the monitor output
- C
Connect the sensor through an RJ-45 Ethernet patch cable and assign it an IP address
- D
Use a USB-to-Bluetooth dongle so the sensor can pair wirelessly
Show answer and explanation
Correct answer: A
Explanation
The best answer is to use a USB-to-serial adapter because RS-232 is a legacy serial communications standard commonly used by industrial equipment, sensors, and older peripherals. Modern desktop systems frequently lack built-in DB-9 serial ports, so USB adapters are a practical and widely supported way to maintain compatibility. In operating systems such as Windows, these adapters typically install drivers and create a COM port that legacy applications can select. This aligns with standard PC support practices and common manufacturer guidance for connecting serial devices to newer systems. The other options are based on different interface types: HDMI/VGA are for video, RJ-45 Ethernet is for network communication, and Bluetooth requires compatible wireless support on both ends.
- A. Correct.
Correct. An RS-232 device that uses a DB-9 connector can commonly be connected to a modern computer by using a USB-to-serial adapter. The adapter installs a driver and exposes a virtual COM port to the operating system, allowing legacy software to communicate with the sensor as if a native serial port were present. This is also consistent with the requirement to avoid opening the PC case.
- B. Incorrect.
Incorrect. HDMI and VGA are video interfaces, not communications interfaces for serial data exchange with an RS-232 sensor. Someone might choose this because of familiarity with adapters in general, but video adapters do not convert a display output into a serial communications port.
- C. Incorrect.
Incorrect. RS-232 serial communication is not the same as Ethernet networking. Although RJ-45 is a common connector for network cables, simply attaching an Ethernet cable does not convert a serial device into a network-capable device. The sensor documentation explicitly requires RS-232, so assigning an IP address would not solve the compatibility issue.
- D. Incorrect.
Incorrect. Bluetooth is a short-range wireless communications technology, but an RS-232 sensor with a DB-9 connector does not become Bluetooth-capable by adding a USB Bluetooth adapter to the PC. A candidate might pick this if focusing only on 'wireless connectivity,' but the sensor must support Bluetooth or use a specialized serial-to-Bluetooth bridge, which is not indicated here.