STP/NTP tutorial

Standardized flow references define the temperature and pressure conditions used to calculate flow readings. This allows flows measured under different conditions to be expressed according to a common standard, keeping readings accurate and comparable.

Changing the standardized conditions (STP/NTP) is easy to do yourself. The tutorial below explains how to configure STP/NTP settings for your Alicat mass flow meter or controller.

Video tutorial

This video shows how to change the STP settings using the display, but these settings can also be changed through serial communications.

Video transcript:

“Hello, I am Michael Whiteside, an application engineer here at Alicat Scientific. Today, I am going to show you how to change your STP and NTP from the front display of an Alicat device. Now let’s get started.

In order to change the standard temperature and pressure or normal temperature and pressure, STP or NTP for short, we will hit menu (bottom right button), basic configuration (bottom left button), and STP/NTP in the top right here.

Now we see there is a list of default values for STP and NTP. If we would like to change this, say we would like to change our STP to 25 degrees Celsius. We will hit change (bottom right button), select digit (top right button), and just move this up to 25 (top left button for ‘up’), hit set (bottom right button).

It will give us a warning that pressing set will affect the device measurements, as the STP is used to convert that volumetric flow into a standardized mass flow. We will hit confirm (bottom right button), and say we like that standard pressure of 14.7, but we want to work in atmospheres.

We will just scroll down to reference pressure units (top middle button for ‘down’), hit change (bottom right button), and we see a long list of different units here. We will scroll down until we hit atm (top middle button for ‘down’). Hit set (bottom right button), and now we see that our STP is set at 25 degrees Celsius and one atmosphere.

That is how to change the STP or NTP on your Alicat device.”

Step-by-step instructions (front panel)

  1. Press menu and select basic config.
  2. Select STP/NTP and, using the up/down buttons, select a category from the displayed list.
  3. Press change to access the parameters display.
  4. Use the Select digit and up/down buttons to make your changes and press set.
  5. You can also change the reference units for temperature or pressure by selecting ref temp units or ref pressure units.

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