Various Timing Standards

UT1 time, or Universal Time, is a timing standard used by astronomers and physicists, directly based on the physical position of the Earth in Space. Any irregularities in the Earth’s rotation affect UT1 time immediately. 

TAI time, or Atomic Time, is a precise scientific time, maintained by averaging the readings of over 400 atomic clocks around the world. These clocks are designed to count in precise seconds and have extremely little drift. Due to irregularities and slight slowdown in the earth’s rotation, UT1 time and TAI time have diverged by approximately 37 seconds at the time of this article.

UTC time is the most commonly used global time standard. Since 1972, UTC uses the same seconds (called “SI seconds”) as TAI time. Thus, without adjustment, UTC time would slowly diverge from UT1. To adjust for this, additional seconds are periodically added to UTC time, called “Leap Seconds.” As of 2024, there have been 37 leap seconds, with the most recent one added in 2016.

The addition of leap seconds is overseen by the International Earth Rotation and Reference Systems Service. The IERS monitors the deviation between UTC and UT1 time, and adds leap seconds as necessary. A leap second may be added up to twice yearly, on December 31 and June 30. A leap second is added onto the very end of each of these days, at 23:59:60 UTC.

Future of Leap Seconds

Leap seconds have long been controversial due to their disruptive effects on telecommunications, satellite systems, and more. At the 2022 General Conference on Weights and Measures, it was announced that by 2035, a new maximum acceptable difference between UTC and UT1 will be defined that will ensure UTC remains unchanged for at least a century. 

Leap Second Pitfalls

In my project mentioned earlier, we found that our PXIe was reporting timestamps in TAI time, whereas our SyncServer, cRIO, and PLC all reported timestamps in UTC.

Beyond this small programming setback, leap seconds have the potential to cause serious issues when not handled intentionally. As leap seconds are added rather infrequently, and many people don’t even know they exist, many systems are not designed to handle a minute with 61 seconds. In the case of high-speed controls and data acquisition systems, the best solution may be to simply not run these systems during the 0-2 minutes per year that have 61 seconds. Otherwise, it is important to understand how your system will behave during these instances and design accordingly.

Read more about how Google applies a “Leap Smear” to reduce the impact of leap second additions.

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This article details how to connect to your B&R device over Ethernet and over a network.

Connecting to a Device over Ethernet

Purpose: Allows file downloads/transfers to the B&R device without re-flashing the Compact Flash each time.

Requirements: B&R device must be physically connected to a computer over Ethernet.

1. To check the current IP address of the device, navigate to Online > Settings.

2. If the desired IP address is different from the current IP address of the device, navigate to Ethernet Configuration (Physical View > Right-click main device > open Ethernet Configuration) and set the IP of device.

3. To ensure that communication will work between the computer and the device, set the computer’s IP address to an IP address with the same first 3 bytes. (Local Area Connection > TCP/IP > Set IP of the device (modify the last digit so that they are not matching).

If the IP address of the device was not changed, the device should be properly connected. Certain options that were previously unavailable (Transfer, Monitor, Stop Target, Warm Restart) will now be available. If the IP address of the device was changed, a new CompactFlash will need to be created. As a workaround to re-creating the CompactFlash, you can change your local settings to match those on the Compact Flash (which will allow for Transfers). Then, you can download the changes to the device IP without re-flashing the CF card. To re-connect, simply repeat steps 2-3.

Connecting to a Device over a Network

Purpose: Allows file downloads/transfer to the B&R device without a direct physical connection, enables send to network locations functionality.

Requirements: Static IP address, B&R device, and computer must both be connected to the same network and network settings.

1. To set the IP address and subnet mask, navigate to the Ethernet Configuration Configuration (Physical View > Right-click main device > open Ethernet Configuration) and set the IP and subnet of the device.

2. To set the default gateway and DNS server address, navigate to AR Configuration (Physical View > Right-click main device > open AR configuration) and set the default gateway and DNS server address.

3. If the device was previously connected to the computer over Ethernet, transfer the new program to set the new network settings. After this transfer, the device will not be connected until the computer’s network settings are set to match the device’s network settings. If the device was not previously connected over Ethernet, create a new CompactFlash for the device to set the new network settings.
    
4. On the computer, set all the same parameters as are on the device. (Local Area Connection > TCP/IP > Set IP of device (same as the device is on), set subnet mask, set default gateway, set DNS server).

Learn more about DMC’s B&R Automation Studio services and contact us today! 

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