HIM
12
The Interface Solution Experts
Smart HART
Loop
Interface and Monitor
seconds. In this example, we will use seven seconds.
The HIM then sees its slave device speak and waits
seven seconds for it to speak again. As long as the
HIM sees a new message from its slave device its
outputs are updated based upon the measured vari-
ables. If the slave device does not speak within the
seven second period, the HIM declares a “No HART”
situation and sends its outputs to the failed communi-
cations values.
To use this feature, proceed with the following steps:
1.
Select the
Listen (Specified Slave) button.
2.
Enter your desired value into the
Timeout Period(s)
text box.
Factory default is 5 seconds. The maximum Timeout
Period is 30 seconds.
3.
Set the exact slave address of the instrument you
wish to monitor. Click the
Set Slave Address button.
This brings up the
HART Slave Device Long Format
Address Settings screen (Figure 8). Enter the required
information into the appropriate text boxes.
The
Manufacturer’s ID and Device Type ID for the
instrument that the HIM will listen to are available from
the HART Foundation website at
www.hartcomm.org
and/or the instrument manufacturer.
Values obtained from the HART website are in HEX
code. The HIM does not use HEX code; you must
convert this value to Decimal code.
Figure 8.
HART Slave Device Long Format Address Settings
Screen
To convert HEX to Decimal code, perform the
following steps:
Access the Calculator feature in Microsoft
Windows® by opening the
Start menu. Next,
select
Programs then Accessories and finally
Calculator.
Ensure that the Calculator is in
Scientific mode.
To do this, select the
View dropdown menu
and choose
Scientific.
Click the
Hex radio button and enter the HEX
code value.
Next, click the
Dec button and the value will be
converted into the Decimal value.
Enter the converted value into the proper param
eter.
The
Device ID Number is the serial number of
the exact device to which the HIM will listen.
4.
Once complete, press
OK.
Download the information to your instrument once you
are finished.
Auto Clear Status Bit
Most HART instruments indicate when a device's
configuration has been changed. This indication
(status bit) can be reset by sending HART command
38–reset configuration changed. Checking the
Auto
Clear Status Bit box causes the HIM to issue this
command whenever the HART instrument it is
monitoring has its configuration changed. However,
the HIM can also be set to alarm on this bit (see
Programming the Alarm Parameters). If the HIM is
both set to alarm and to auto clear, then it will do
both–going into alarm mode and resetting that
indication.
Quick Read/Set
The
Quick Read button causes the PC Configuration
Software to read the communications information from
the attached HIM; the
Quick Set button causes the
software to configure the HIM’s communications
settings to match those of the PC Software.
