NI-9467 Getting Started

NI-9467 Overview

The NI-9467 is a stationary GPS timing module for C Series platforms. It provides accurate timing and geographic location information to the C Series host, which enables synchronization of C Series systems.

Start-Up Behavior

At start-up, the NI-9467 automatically begins determining its location through a process known as self-survey. During the self-survey, the module computes a location fix every second and averages the locations at the end to obtain a more accurate location. After the self-survey, the NI-9467 no longer computes new location fixes; it uses its known location and satellite signals to generate accurate timing signals.

Like all GPS receivers, the NI-9467 requires GPS satellite ephemeris and almanac data to compute accurate time and location. The ephemeris is detailed orbital information about each satellite (where each satellite is expected to be at a given time). The almanac data describes the general health of each satellite (for example, the receiver must not use signals from satellites marked as unhealthy) and contains coarse orbit information. The GPS satellites broadcast the ephemeris and almanac data every 30 seconds. Therefore, it usually takes approximately 30 seconds for it to receive the ephemeris and almanac data and start computing location and timing fixes.

Status LED

The NI-9467 has a front panel LED to indicate status. The following table describes the meaning of each LED pattern.

Conditions LED State
Normal operation Solid green
Performing survey Blinking green
Not enough or no satellites Blinking yellow
Antenna error (no antenna or over-current) Solid yellow
Unconfigured Off
Note Although the module may not detect the presence of very low-power GPS antennas, it can still function correctly. Note that the LED and software may report antenna error under these conditions, and if the current consumed is close to the detection threshold the LED may flicker. Refer to the NI-9467 Specifications for more details.

Connecting the NI-9467

The NI-9467 has one SMA female connector on its front panel for a GPS active antenna. The connector provides a DC voltage to power the antenna and also serves as input for the GPS RF signal.

Installing the Antenna

Notice NI recommends installing a lightning arrester with the GPS antenna. Adhere to local code requirements for lightning arresters or other lightening protections when installing the NI-9467 with an antenna outdoors.

The embedded GPS receiver in the NI-9467 requires signals from several satellites to compute accurate timing and location. The more satellites available to the receiver, the more accurately it can determine time and location. Therefore, the antenna location should be such that it receives signals from the greatest number of satellites possible. As the number of satellites visible to the antenna decreases, the synchronization performance may also decrease. Choose the antenna location so that the antenna has a clear view of the sky. There is no strict definition for a clear view of the sky, but a suitable guideline is that the GPS antenna should have a straight line of sight to the sky in all directions (360°) down to an imaginary line making a 30° angle with the ground. Locations far from trees and tall buildings that could block or reflect GPS satellite signals are best.

Maximum Cable Length

Maximum cable length depends on the GPS antenna gain and the cable’s loss per unit of distance. National Instruments recommends a GPS signal strength of between -135 dBm and -120 dBm at the NI-9467 SMA input. GPS signal strength on the Earth’s surface is typically -130 dBm. Targeting a signal strength of -125 dBm at the SMA input, you can compute the maximum cable length as:

  • Max_cable_loss = -130 dBm + antenna_gain - (-125 dBm)
  • Max_cable_length = Max_cable_loss / (loss_per_unit_of_distance)

For example, if you use an active antenna with gain of 28 dB and RG-58 cable, which has a rated loss at 1.5 GHz of about 0.8 dB/m (24.5 dB/100 ft), the maximum cable length you could use is:

  • Max_cable_loss = -130 dBm + 28 dB - (-125 dBm) = 23 dB
  • Max_cable_length = 23 dB / (0.8 dB/m) ≈ 29 m

Sleep Mode

This module supports a low-power sleep mode. Support for sleep mode at the system level depends on the chassis the module is plugged into. Refer to the chassis manual for information about support for sleep mode. If the chassis supports sleep mode, refer to the software help for information about enabling sleep mode. Visit ni.com/info and enter cseriesdoc for information about C Series documentation.

Typically, when a system is in sleep mode, you cannot communicate with the modules. In sleep mode, the system consumes minimal power and may dissipate less heat than it does in normal mode. Refer to the NI-9467 Specifications section for more information about power consumption and thermal dissipation.

Notice that when the NI-9467 is in sleep mode, the GPS receiver is not powered and stops tracking satellites. When the module exits sleep mode and power to the GPS receiver is restored, the module goes through the normal power-up process, which includes the ephemeris/almanac data acquisition and self-survey process. Therefore, it can take approximately 30 seconds before usable timing and location signaling can be generated. Refer to Start-Up Behavior for more information.