Network Time Protocol (NTP)
The Automation1 controller uses the system clock to generate a timestamp when it writes information to a file. General clock drift has an effect on all clocks, regardless of their local system. Thus, you might encounter a small quantity of drift each day, which can range from a few milliseconds to a few seconds. If the clock is not synchronized to an external time source at regular intervals, this small quantity of drift might increase over time to a large quantity of minutes. The quantity of clock drift that occurs in a system can change based on a wide range of environmental factors, such as temperature. If you do not power on the system for long periods of time, you might see a large difference between the system clock and the actual time.
As an alternative to manually setting (see Date and Time Configurations) or re-synchronizing the clock (such as to a PC for drive-based controllers), you can configure and use the Network Time Protocol or NTP. This networking protocol is frequently used and supplies automatic, external clock synchronization between a client (local system) and an NTP time server. NTP corrects time differences by using time steps or a process named slewing, which makes small adjustments to the clock rate to gradually decrease clock drift. The greater the time difference between the client and server, the longer it will take to correct clock drift. You can configure the NTP with all of the methods that follow:
- PC-Based Controllers: Configure the NTP by using standard Windows menus.
- Drive-Based Controllers: Configure the NTP by using Machine Setup (see the Controller milestone) or the Console.
To use the Network Time Protocol (NTP), you must specify the hostname or IP address of one or more time servers that you want to synchronize with. The first time that NTP connects to a time server, the controller will do one full synchronization of the system clock for immediate synchronization.
Before you use the Network Time Protocol (NTP), make sure that you know the important information that follows:
- Do not try to manually adjust the system clock while the Network Time Protocol (NTP) is running. This keeps automatic time synchronization accurate. If you try to do this, a controller error will occur.
- Aerotech recommends that you configure three or more time servers. The Network Time Protocol (NTP) might reject time sources that it determines to be inaccurate.
WARNING: When you use an internet-based Network Time Protocol (NTP) time server, your system can be exposed to security risks. Make sure that the time server you connect to is dependable and from a trusted source. You are responsible for any problems that occur because of a compromised or defective time server, which can include system compromise, data loss, and service disruptions.
As an alternative to using an internet-based Network Time Protocol (NTP) time server, you can configure a local NTP time server on your network. Before you do this, Aerotech recommends that you contact your IT department to make sure there is no other local NTP server established on your network.
