- I've had several requests
to give an overview of how to configure a HART device using a handheld programmer. So in the next few
minutes, I'll show you how to correctly wire a HART
device on the bench, connect the handheld, and access
the configuration options. I'll also explain some of the
different terms you'll hear and show you an alternative
option to a handheld. Let's get started. This is what you'll need: A HART device, a 24 volt DC power supply,
a HART handheld programmer, a multi-meter and most importantly, a 250 ohm resistor. Now if you're making a scrunchy
face about the resistor, let me show you why you need this. Most HART devices are loop-
powered, meaning they get power from the PLC card they're connected to. The PLC input essentially
has a power supply and some input impedance built
in- normally around 250 ohms. If you remember from one
of my previous videos, the HART signal is
superimposed onto a 4 to 20 milliamp signal, and is
actually a small AC voltage. If you're familiar with basic electronics, you know that you have
to measure the voltage across a resistor. Now let's wire this up
and see what we get. (light upbeat music) All set! I created a loop
with the HART device, power supply, and load resistor. And I had my trusty multi-meter in the loop so we can monitor the loop current. Now that our loop is
working, we can connect our handheld programmer
across the resistor. But before I start
programming, let me explain a little bit about handhelds. When you buy one of these,
it will be delivered with a library of device
descriptors, or DDs, already loaded. Every HART device has a unique DD file that contains the menus, fields, or wizards that are needed to configure the device. So when a new device is
released to the market, you will need to update
the library on your handheld with the DD for that new device. Occasionally, a device may also be updated with new functionality that requires a new or updated DD, so you might have to update your handheld then too. But in the instance you
don't have the correct DD for your device, don't fret
as there is a generic DD that allows you to do basic
configuration for any device. Okay, so now we want to
tell the handheld to look for connected devices so
it will start scanning each HART address. When it finds a device, it
will pull up the correct DD- and we're off. Now keep in mind that HART
communicates at only 1200 baud, so don't be surprised when it
takes a few seconds to load. Now the DD for the device
is loaded, and in this case we're connected to a radar level gauge. You can see the process
variables displayed. If we go into the configuration
menus, we can access basic set-up parameters. For instance, we can choose the media type, whether we are measuring
a liquid or a solid. We can also select the tank shape and calibrate empty and full levels. In the extended configuration
menu, we can set up output and signal dampening and parameters for preventing false readings. So, device configuration using
a handheld is relatively straight-forward, however, a
handheld is a pretty expensive piece of equipment, clocking
in at about $8,000. Now if you're suffering from sticker shock, it's because the handheld
is approved for use in hazardous areas and
must be intrinsically safe. Just ask my friend here. Another option for bench top
configuration is a USB modem. This cost-effective device,
along with my laptop, can do the same functions as the
handheld. This software package uses
the same type of DD library as a handheld, and here
you can see the options look identical to what's
accessed using a handheld. So that's it! Configuring a
HART device with a handheld or USB modem is pretty simple. Just remember the number
one thing that people forget is that little 250 ohm resistor. Want to learn more about HART? Check out our other videos that are linked in the description below. If you like what you saw,
smash that like button and share it with a colleague. And let me know if you
want to see something else- My contact information is
also in the description. Until next time.
