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Devin Seran

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Vacuum Gauge Series: Thermocouple Gauge Tubes

Posted by Devin Seran on Mon, Apr 12, 2021 @ 04:02 PM

Vacuum Gauge Series - Thermocouple Gauge Tubes Fun FactTeledyne Hastings was founded in 1944 as The Hastings Instrument Company by Charles and Mary Hastings. The late 1940s saw the introduction of thermal sensing technology at the young company which became the foundation for many early Hastings instruments such as air velocity indicators, thermal mass flow meters, stack emission monitors and, of course, the thermopile vacuum sensor.

By 1964, Hastings Instruments had grown into one of the leading vacuum and thermal mass flow instrument companies in America. Today, our popular Thermocouple Vacuum Gauge Tube product lines, including the DV-4, DV-5, and DV-6, are trusted around the world where repeatable, rugged, and dependable vacuum measurement is needed. Based in Hampton Virginia for over 75 years, the highly skilled employees at Teledyne Hastings are dedicated to delivering the highest quality thermocouple vacuum gauge tubes.

How does a thermocouple gauge tube work?

How a thermocouple vacuum sensor works is simple! As an example, let’s take a look at the DV-6R, shown in the diagram to the right, along with the representative schematic.

There are three thermocouples shown (A, B, and C) in the diagram. Now, an individual thermocouple consists of two dissimilar metals which are joined together at a junction. At the junction, there will be a small voltage which is a function of temperature. During operation of the gauge tube, thermocouples A and B are resistively heated inside the gauge tube’s housing. Now, since the wires connected to A and B thermocouples are exposed to the gas in the vacuum, thermal energy will be transferred away from the wires at a rate which is dependent on the number of collisions between the gas and the wires and thereby depends on the pressure inside the tube.

Vacuum Gauge Tube Illustration DV-6R-resized-183

Let’s consider two extremes. In high vacuum, where the pressure is very low, there will be fewer gas collisions with the wires and the tube’s voltage output will be relatively high. (Higher temperature corresponds to higher thermocouple output). Now, towards high pressures, more gas results in more thermal energy being carried away from the wires and the thermocouples run at a lower temperature and so give a relatively low output.

 

How to use a thermocouple vacuum gauge tube:

To use a thermocouple vacuum gauge tube, you must connect the gauge tube with an instrument that correctly excite the tube’s wires and also converts the output of the gauge tube to the correct pressure measurement. Note that new gauge tubes from Teledyne Hastings are manufactured to the highest quality and are tested to be very repeatable from tube to tube.

So let’s take, as an example, the use of a DV-6R vacuum gauge tube with a DCVT-6 panel meter or HPM-4/5/6 handheld meter. Both the DCVT-6 and HPM-4/5/6, out of the box, are setup to provide the correct activation to the DV-6R. The output from the gauge tube is then monitored by the instrument and the correct vacuum level is displayed for the user.

In the case of the DCVT, two contact relays are available to the user for process control. The user can simply dial up the desired setpoints and the dual relays will independently toggle when the vacuum setpoint has been crossed. You can now easily understand how Teledyne repeatable gauge tubes will lead to repeatable process control! The DCVT also provides serial communication (RS232) and linearized analog output options (0-1 VDC, 0-5 VDC, 0-10 VDC, 4-20 mA).

Teledyne Hastings' Vacuum Products
DCVT-6 HPM 4/5/6 DV-6R DV-6S
Model DCVT-6 Vacuum Gauge

HPM

DV-6R-resized-183 DV-6S-1

Application Example:

Gas Plant Tanks 182395563There are many applications where a thermocouple vacuum gauge tube is an excellent choice. One example we will briefly discuss in this short blog is vacuum insulation or vacuum jacketing. The technique of using a vacuum guard or barrier to thermally insulate a cryogenic or refrigerant tank is straightforward: remove the air from around an object and eliminate conductive heat transfer. The better the vacuum is then the better the vacuum insulation. To effectively measure pressure in the mTorr range, a vacuum dial gauge is simply not sensitive enough.

A vacuum reading can be obtained from any of the DV-6 tubes using either a dedicated electronic display or handheld battery-operated readout. The Hastings’ DCVT provides continuous monitoring with an easy to read LED display. For periodic vacuum checking of one or more tubes, the hand-held HPM 4/5/6 is recommended. For convenience, it is powered by a 9V battery and can be connected to any DV-6 tube for an instant reading. To ensure the most accurate measurement, the DB-20 Reference Tube (with NIST Traceable calibration) can be used to validate the electronic calibration.

If you would like to learn more about vacuum jacketing click here.

For more information about any of our thermocouple sensor series or vacuum gauges, we are here to help. In addition to LiveChat on our website, you can contact us at hastings_instruments@teledyne.com or call 757-723-6531 (800-950-2468) or click the button below.

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Tags: vacuum gauges, Thermocouple Gauge Tubes

Introducing our Newest Product - THCD-401 4-channel power supply

Posted by Devin Seran on Thu, Mar 05, 2020 @ 03:51 PM

Figure 1- THCD-401 Teledyne Hastings is proud to announce our newest 4-channel power supply, controller and display, the THCD-401. The THCD-401 provides both ±15 VDC or 24 VDC to power our mass flow controllers, flow meters, vacuum gauges and pressure transducers. Feedback from connected devices is displayed on the bright, front panel LED display in 6-digit resolution, making open and closed channels easily identified at a glance. The THCD-401 can set a relay point for control of other processes and has a high accuracy of ± (0.02% of Reading + 0.01% of Full Scale). Custom configuring our products to customer needs is our specialty. Your THCD-401 can be factory configured to match the gas, range, units and the output of your instruments for out-of-box functionality.

What’s Improved?

In short, the THCD-401 was designed for exceptional user access and control.  The addition of a circular touch pad simplifies navigation through the unit’s various menu options, while left and right arrow keys allow easy selection of digits to be changed. Calibration is no longer needed for various levels of input voltage and built-in fuses provide additional surge protection.  Back panel communication ports have been streamlined and a USB-C and Ethernet port for serial communication have been added. 

Ethernet Starburst-1The addition of Ethernet communication provides access to the newest feature that the THCD-401 has to offer; the internal web server! The web server can be accessed by entering the IP address of the THCD-401 into a browser’s address bar (requires static IP address configuration on the network prior to use). While the web server feature works best in Mozilla™ Firefox®, it can be accessed via any browser you choose.  Figure 2 shows the web server interface with applications along the top navigation bar and a live data stream for remote read.

The web server allows you to name channels and adjust the range or units based on your device and the full scale (V) voltage output that it sends. This enables users to see the flow rate of a flow controller or meter, as well as the ability to OPEN/CLOSE all channels at the click of a button. Other applications include linearization, setting of a relay point and finding the total amount of gas that has passed through the device using the totalizer function.
Figure 2 - New web browser interface for THCD-401

It should be noted that while all these advanced features are available via the web server (Ethernet) connection, the THCD-401 also offers direct access to each via the front panel display menus using the circular touch pad.  This allows for quick and convenient setup of the channel’s full scale and range(V) for new devices.

If a relay point has been tripped, it will be indicated to the left of the channel’s name on the THCD-401 display. The display will also show the current mode of the set point, if it is not configured in AUTO mode. In OPEN mode, the set point outputs a voltage greater than the full scale of the device. In CLOSED mode the set point outputs a voltage less than the minimum output voltage of most devices. AUTO mode is dependent on the user defined set point configured through the THCD-401 physical buttons, digital communication or external input. 

More Information:

The THCD-401 was designed to be a highly flexible and multi-featured process display controller that can be panel mounted and capable of interfacing to an assortment of meters, controllers and gauges.  A powerful upgrade from the previous THCD-400 model, the THCD-401 adds digital communications, a bright LED display and a variety of customizable options to an already time-tested platform. To learn more about the
THCD-401 or any of our other vacuum and flow products, contact us at hastings_instruments@teledyne.com, call 1-800-950-2468, or click the button below.

Interested in THCD-401

Tags: Power Supply