Maximum network size and publishing policy settings

The maximum network size for use with Emerson's Smart Wireless Gateway is defined in Table 1.

Table 1. Maximum network size
Number of wireless devices Update rate (in seconds)
12 1
25 2
50 4
100 8+

You can have up to 100 CSI 9420 devices on a single gateway, as the HART variables (i.e. scalar values) never have an update rate faster than 60 seconds. The update rate is typically once every 60 minutes.

The maximum network size decreases as you add different types of wireless devices to your network and when you collect high-resolution data. For example, if 5 temperature transmitters are broadcasting at a 1 second update rate, you will be able to add fewer CSI 9420 devices on this gateway than if the network contained only CSI 9420 devices. When you collect high-resolution data from a CSI 9420, such as vibration spectra and waveforms, the network can accommodate fewer wireless devices.

AMS Machinery Manager controls spectrum and waveform collection. The software features a publishing policy that limits the amount of data broadcast from a single device or over a single gateway. Figure 1 shows the menu to configure the publishing policy in the (Modbus) Data Import program. Table 2 shows the recommended (default) publishing policy settings. The default settings allow only 4 devices to send a full set of diagnostic data in a 24-hour period and no device will send data more often than every two weeks. This ensures that diagnostic data does not compete with process data, and that no single device dominates the available bandwidth.

Figure 1. CSI 9420 publishing policy menu

Table 2. Recommended (default) publishing policy settings
Network size Interval






N N/4 days

(but never less than 14.00:00)

N*8 8 High-resolution data limited only to 4 devices per day with most frequent collection interval of 2 weeks for 1-64 devices.

After 64 devices, the collection interval increases to (N/4) days.

AMS Machinery Manager v5.61 features an auto-calculate button that populates the CSI 9420 Publishing Policy menu with default values shown in Table 2.

If a gateway is dedicated to vibration monitoring and will not be routing any process data, then you can customize the publishing policy to allow more diagnostic data to be collected. Follow these steps:

  1. Use the settings in Table 3 and Table 4 to achieve the maximum network size as indicated.
    Table 3. Maximum network size when collecting velocity and PeakVue spectra only (no waveforms)*
    Network size Interval


    Gateway credits Device credits
    12 1.00:00 48 4
    25 3.12:00 100
    50 7.00:00 200
    100 30.00:00 400
    *Set-up for average velocity spectrum and PeakVue spectrum.
    Table 4. Maximum network size when collecting velocity spectrum and PeakVue waveform*
    Network size Interval


    Gateway credits Device credits
    12 1.00:00 72 6
    25 3.12:00 150
    50 7.00:00 300
    100 30.00:00 600
    *Set-up for average velocity spectrum and PeakVue waveform.
  2. Set up efficient data collection as follows:
    • Use/create a well-formed network which conforms to best practices as described in the WirelessHART System Engineering Guide.
    • Collect an averaged spectrum for overall vibration (recommended). Do not collect the waveform used to calculate the overall vibration value in the device itself. Starting in AMS Machinery Manager v5.61, the spectrum can be 400 lines instead of 800 lines, which further increases the availability of bandwidth. If you require the waveform from overall vibration, you can collect it on demand.
    • For PeakVue, collect the waveform; the spectrum is always collected with the waveform. You need the waveform in order to use Auto-correlation to look for periodicity in the waveform. Auto-correlation helps you distinguish between impacting that is the result of under-lubrication or pump cavitation versus actual bearing damage.