Help Us Out
We’re looking for customers to test this new WinDaq software approach for defining engineering units and give us their opinions. Currently the new code is available only for starter kits, so anyone with a DI-194(RS), -154RS, -148U, -148U-SP, -158U, -158UP, -145, -149, or DI-155 qualifies. To sign up, please leave a comment on this blog post with a valid email address, and we’ll follow up with instructions. Note that the new code doesn’t yet replace the other engineering unit scaling options. So, if you hate the new approach you have time to tell us why and have us fix it before it does. Finally, we’ve tested this code and found it to work well, so we hope your evaluation applies only to look and feel. Of course, if you trip on a bug please let us know.
What follows should give you a good feel for why we’re making this change and why its better. Of course, feel free to post any questions you may have in the comments section.
Engineering Unit Scaling Background
The first thing that most data acquisition and data logger equipment users want to do after they acquire analog data is to scale it into meaningful units. To most, acquired data displayed in volts is next to meaningless. They need the ability to translate volts into meaningful measures, like PSI, Newtons, ft-lb, mmHg, etc. These are often referred to as engineering units (EU), and the process of converting voltages applied to the input into meaningful measures like these is referred to as engineering unit scaling. Of course, DATAQ Instruments’ popular WinDaq application supports this feature, but you’ve let us know that the procedure, as well as what we call it, needs improvement.
You talked. We listened.
We heard you. Based upon countless conversations with you, it was clear that our current High/Low method as well as the Fixed method of converting to engineering units was neither intuitive nor easy to use. We also sensed that we confused our customer base through our use of the word calibration to refer to EU scaling. Many customers rightfully feared that they would change the actual calibration of the data acquisition unit if they used these features. None of this is good news for a feature that is so crucial to data acquisition and data logging operations.
A New Engineering Unit Scaling Dialog Box
We’ve responded with a fresh approach to engineering unit scaling that we hope you will view as a major step forward for WinDaq ease-of-use.
Nearby you will see a graphic image of our new Engineering Unit Settings dialog box, which will eventually replace our current High/Low and Fixed dilaog box approaches. I hope at first glance that, aside from minor questions, it’s obvious how to use it. In the most basic applications, you know the relationship of volts to engineering units and you simply define that relationship using the supplied dialog boxes. Some examples:
- 10V equals 500 PSI and 0V equals zero PSI.
- Under the Volt column, you’d set Upper Level equal to “10” and Lower Level equal to “0”
- Under the EU column, you’d set Upper Level equal to “500” and Lower Level equal to “0”
- Set the EU Tag dialog box to “PSI”
- Using a 250-Ohm resistor on a process current loop where the sensor’s output is 300 lbs at 20 mA and 0 lbs at 4 ma
- Since the 250-Ohm resistor converts the 4-20 mA signal to 1-5 V…
- Under the Volt column, you’d set Upper Level equal to “5” and Lower Level equal to “1”
- Under the EU column, you’d set Upper Level equal to “300” and Lower Level equal to “0”
- Set the EU Tag dialog box to “LBS”
Some Additional Features
As you study the new Engineering Units Settings dialog box you’ll notice some interesting items starting with the eyedropper icons adjacent to the Volt data entry boxes.
We’ve noticed that many WinDaq users simply do not know the relationship of volts output from the sensor versus engineering units, so they derive the relationship empirically. Using the example of a load cell with an unknown output versus pounds of applied force, they’ll apply no load, then measure and record the voltage output. Then they’ll measure and record the output with a known load applied. The two recorded voltage values versus applied load can be entered in the appropriate boxes to define the relationship.
The eyedroppers eliminate a couple steps. They allow you to sample the current value of the applied voltage when you click the icon, and have it automatically displayed in the Volt box for either the Upper or Lower value depending upon the applied load. Continuing with the example, you’d apply no load and click the Lower eyedropper so the software will acquire the lower voltage value and display it automatically in the Lower box for voltage. Then you’d enter zero for the lower EU value. Next, you’d apply your known load and do the same for the Upper values. Enter your EU Tag and you’re done. As you can see for this calibration method, using the eyedroppers saves time and greatly reduces the possibility of human error.
Finally, there’s the Set Zero button that allows you to instantly compensate for zero offsets from your measurement. How many times have you carefully calibrated a system only to see a slight offset in the result when you apply zero engineering units? It’s very common. You can apply zero engineering units to your sensor and then use the Set Zero feature to instantly force the offset to zero when you click the button.
In the final version that we release to everyone, an additional button labeled Help (not available in this beta version) will provide a dedicated help reference just for the Engineering Unit Settings dialog box.