IMPAC pyrometers series IN 5 plus
19
9.2.2
Subrange
You have the opportunity to choose a subrange (minimum 51°C) within the basic measuring range of the
pyrometer. This subrange corresponds to the complete analog output. The lower value (0 or 4 mA) describes
the beginning of this measuring range, the upper value (20 mA) the end of the range.
Additionally with the setting of a subrange it is possible to fulfill the requirements of the “auto” clear mode of
the maximum value storage (see 9.2.1 Maximum / minimum value storage).
9.2.3
Baud rate
The transmission rate of the serial interface in Baud (Bd) is dependent on the length of
the cable. A standard cable length with RS232 for 19200 Bd is 7 m, with RS485 2 km.
The baud rate is reduced by 50% if the transmission distance is doubled.
9.2.4
Address
For the connecting of several pyrometers with RS485 with one serial interface it is nec-
essary to give each instrument an individual address for communication. First it is nec-
essary to connect each single instrument to give it an address. After that all instruments
can be connected and addressed individually. If parameters may be changed simulta-
neously on all pyrometers, the global Address 98 can be used. This allows you to pro-
gram all pyrometers at the same time, regardless of the addresses that have already been assigned. If the
address of a pyrometer is unknown, it is possible to communicate with it using the global Address 99 (con-
nect only one pyrometer).
9.2.5
Ambient temperature compensation
Each object has an emissivity
ε
(maximum 100%). If the measured object is not transparent and has an
emissivity of less than 1 (as in most cases), a portion of the resulting radiation will be reflected.
For bright, smooth surfaces, such as mirrors, the reflected radiation is more focused; on rough, harsh sur-
faces it is diffuse. The rate of diffuse reflection is, in this case (1 -
ε
).
If the measured object’s temperature is the same as the ambient temperature (this is most often the case),
you only need to set the emissivity on the pyrometer (when using the InfraWin program the off-set compen-
sation for the ambient temperature must be in “auto“; see 10.7 Basic settings).
If the object to be measured is in an oven, where the temperature is higher than the ambient temperature, a
portion of the radiation, corresponding to the rate of diffuse reflection, will be “reflected“ by the measured
object to the pyrometer, resulting in an inaccurate reading (the reading will be too high due to the oven tem-
perature).
In this case, it makes sense to activate the off-set compensation for the ambient temperature (in the parame-
ter window of the InfraWin program: Compensating for the off-set of the ambient temperature switched to
“man.“ (= manual) and then enter the ambient temperature value (in this case, the oven temperature) in the
corresponding field (also see section 10.7 Basic settings). The program also makes a compensation calcu-
lation in order to display the correct temperature.
Be aware that the accuracy of such a correction is highly dependent on accuracy of the emissivity value that
was set. The off-set compensation for the ambient temperature uses the rate of diffuse reflection when per-
forming its calculation. If you alter the emissivity (
ε)
, you are also altering the rate of diffuse reflection (1 –
ε
)
and in turn, the displayed temperature. The following observation shows how a faulty emissivity reading in
conjunction with the compensation for the ambient temperature affects results:
Entry of
ε
= 91% instead of 92% indicates:
A relative change in emissivity of 1.1 %.
Likewise the assumed rate of reflection changes from 8 % to 9 %.
This results in a relative increase in reflection of 12.5 %.
This change also impacts the displayed result, thereby causing a fairly inaccurate compensation calculation.
For hot environments, this calculation will probably serve as a much more accurate assessment than the
standard calculation, which assumes that the ambient temperature is the same as that of the object meas-
ured.
Settings via
interface:
1.2 kBd
.
.
.
19.2 kBd
Settings via
interface:
00
.
.
.
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