Power Considerations
- Updated2023-03-14
- 4 minute(s) read
Power Considerations
The TestScale backplanes have two four-pin power connectors to supply power to the entire TestScale assembly.
- Vsup—Supplies power to the backplane components and to all module slots.
- Vaux—Increases available current to any installed modules with high-power requirements, such as programmable power supplies. Refer to your module specifications for Vaux power consumption information.
Calculating TestScale Power
Requirements
NI recommends the following 24 V DC power supplies: PS-15, PS-16, or PS-17 which vary based on current output capability. Any power supply used to provide power to the TestScale assembly must account for the total estimated power consumption and desired DC voltage for your application.
Every backplane and I/O module has different power consumption requirements as detailed in their model specifications. Depending on the I/O modules selected for use with the backplane, you must determine if the selected DC Power source can provide adequate power to the entire system in a single backplane. Use the following calculation to determine the power requirements of your TestScale system configuration.
- Referring to your I/O module and backplane specifications, add the total power consumption
of all components in your TestScale configuration, where
Y is the total power consumption from Vsup of all I/O modules and Core Module
Z is the total power consumption from Vsup of the backplane
- Use the following equation to determine the total power required for Vsup:
- Determine the power required from Vaux (Power_Vaux) by adding up the power
specification values from the respective module specifications.Note Both the power rails for Vsup and Vaux have the same voltage range specification of 11 V to 28 V. Both power rails can be sourced separately from separated external power sources with different voltage settings or can be combined to use a single power source with the same voltage setting.
- When using a single power source, ensure that Power_Vsup +
Power_Vaux is below the maximum output specifications of the
external power supply.
When using separate power sources, ensure that each individual calculation for Power_Vsup and Power_Vaux are below the maximum output specifications of the external power supply.
- Ensure the maximum current derived from the maximum total power consumption—where Current = Total Power/Selected Voltage Output for each rail (Vsup and Vaux)—is less than the current rating of the power connector (11 A) when using either a single backplane or when using multiple backplanes in a daisy-chained configuration.
Connecting Multiple TestScale
Backplanes
Daisy-Chaining from a Single Power-Supply
You can connect multiple backplanes in a daisy-chain power supply configuration through the Power Output connector on the backplane using a single DC power source. The selected power source must be capable of providing the total power for all backplanes and their associated module configurations. To determine the total power requirements for each backplane in the daisy-chain configuration, repeat the calculations for each of the following items as detailed in the Calculating TestScale Power Requirements topic.
- Total power consumption for the backplane, core module, and I/O modules
- Total power consumption of Vsup
- Total power consumption for Vaux
Ensure the external power source connected to the primary backplane in the daisy-chain configuration can supply the total required power while also ensuring the total current sourcing into backplane is less than current rating of power connector (11 A).
Daisy-Chaining from a Single Host Computer
You can control multiple backplanes with a single host computer by connecting them in a daisy-chain configuration through a USB connection. The number of TestScale backplanes that can be connected together is dependent on the USB topology. The TestScale backplane has an integrated USB hub, which the USB standard limits to five daisy-chained hubs—including the host computer's internal hubs. When connecting multiple TestScale backplanes, please note the number of USB buses being used. The actual throughput performance varies depending on the system setup and composition, such as the number of modules, sample rate, host, and so on.
The following figures demonstrate the connections for daisy-chaining multiple TestScale backplanes.