This article explains how to connect a serial monitor to a USB port

If you have a serial touch monitor and your computer system only has a USB port, there are two methods to solve this problem.

1. The best solution is to purchase an add-in serial port card; they are offered in a range of prices and quality and can be purchased from several vendors. When purchasing an add-in serial port card, we recommend that the serial ports be true UART (Universal Asynchronous Receiver Transmitter) devices. Typically this will be denoted in the product specification as a UART 16550. Beware of products that claim UART compatible or 16550 compatible.

2. Another solution is to use a USB to serial converter to add serial ports to a system, but we have found that the majority of these devices do not function well with a data-intensive device such as an Elo touch monitor. Some USB to serial converters simply do not work with Elo touch monitors; others may work with Windows 2000 and XP but not with earlier operating systems (or vice versa). We have also found that models and availability are constantly changing. Elo does not recommend using USB to serial adaptors with its products, and cannot offer technical support if such devices are used.