Dwyer PMT2 Serie Manual Del Usuario página 4

SET UP
Mounting
Make sure the PMT2 is securely mounted to the stack, pipe or duct to prevent vibration
during operation. Make sure the transmitter is grounded properly.
Control Signal Set Up
Check the power supply wiring to make sure the polarity is correct before powering
the PMT2. Turn the power on to the transmitter and turn the Range and Test selector
switch to 4 mA (position 2). The PMT should output 4 mA, check the output with a
multi-meter or at the device (PLC, Display, etc.) receiving the output signal. Once it is
verified the 4 mA signal is being received, switch the Range and Test selector switch to
20 mA (position 1) and repeat the process. If the output is 0 mA, make sure the power
supply is on and check for loose wires.
Range and Test Selection
When selecting one of the 6 available ranges, the baseline and maximum peak signals
that take place during filter cleaning must be taken into account. The selected ranges
should have enough resolution to monitor the baseline and capture the maximum
peaks during a cleaning cycle. The four linear ranges output 4 mA at 5 pA and 20 mA
at maximum range. The two logarithmic ranges have finer resolution at the low end of
the ranges and less at the high end.
Switch Position Range
1 Test
2 Test
3 5 to 100 pA
4 5 to 500 pA
5 5 to 1000 pA
6 5 to 5000 pA
7 Log 5 to 500 pA
8 Log 5 to 5000 pA
Note: Position 9 and 0 are unused.
Table 2: Range and test switch
Output
20 mA
4 mA
5 pA = 4 mA
25 pA = 8 mA
50 pA = 12 mA
75 pA = 16 mA
100 pA = 20 mA
5 pA = 4 mA
125 pA = 8 mA
250 pA = 12 mA
375 pA = 16 mA
500 pA = 20 mA
5 pA = 4 mA
250 pA = 8 mA
500 pA = 12 mA
750 pA = 16 mA
1000 pA = 20 mA
5 pA = 4 mA
1250 pA = 8 mA
250 pA = 12 mA
3750 pA = 16 mA
5000 pA = 20 mA
5 pA = 4 mA
16 pA = 8 mA
50 pA = 12 mA
158 pA = 16 mA
500 pA = 20 mA
5 pA = 4 mA
28 pA = 8 mA
158 pA = 12 mA
890 pA - 16 mA
5000 pA = 20 mA
1000 PA
750 PA
EMISSION
SPIKE ALARM
500 PA
BASELINE
ALARM
5 PA
LOGARITHMIC RANGE
The logarithmic ranges offer a prolonged low-end of the scale while the high-end of the
range is compressed. This offers better resolution for the baseline monitoring and still
allows the operator to see the particulate spikes during cleaning cycles. Logarithmic
ranges are recommended for filter bags since they have a greater tendency for
particulate spikes during cleaning cycles.
LOGARITHMIC RANGE EQUATIONS
)
(
(M-4)
pA = 10 x R + 0.699
16
pA = Measured (pA) Picoamps
M = Measured (mA) Milliamps from the PMT2
R = 2 (for Logarithmic Range 5 to 500 pA)
R = 3 (for Logarithmic Range 5 to 5000 pA)
Example 1: Logarithmic Range 5 to 500 pA with current output of 12 mA:
)
(
(12-4)
pA = 10 x 2 + 0.699
16
pA = 50
Example 2: Logarithmic Range 5 to 5000 pA with current output of 14 mA:
)
(
(14-4)
pA = 10 x 3 + 0.699
16
pA = 375
SETTING EMISSION LEVEL ALARMS
The PMT2 will provide a 4-20 mA signal based on the range selected at set up. Alarms
can be programmed in the PLC or control system based on the 4-20 mA signal from
the particulate transmitter.
It is suggested to set two alarm set points. One alarm set point to monitor the emission
spikes and the second alarm to detect an increase in the baseline.
The alarm monitoring the emission spikes should be set to identify changes in the
spikes caused by the cleaning cycles. As filters become worn, the spike's height and
duration will increase. The emission spike frequency will also increase because the
filters will require more frequent cleaning as they wear out. If there is a continuous
output above the emission spike alarm, it is more than likely a filter has torn and should
be changed right away.
The baseline alarm should detect an increase in the baseline reading. The type of
dust collector and facility regulations will dictate where the baseline alarm has to be
set. Typically the baseline alarm should be set 4 to 5 times over the initial baseline
reading measurement when filters are first installed. So, if the baseline is 10 pA the
base line alarm should be set between 40 pA and 50 pA. It is recommended to set a
time delay in the PLC or control panel alarm to prevent false alarms during cleaning
cycles. When the output signal from the PMT2 is continuously above baseline alarm
it is time to replace the filters. If the emission spikes have increased yet the baseline
remains unchanged, it's an early indication that the filters are starting to wear out and
will need to be changed soon.
INCREASED SPIKE
BECAUSE OF
FILTER WEAR
SPIKES CAUSED
BY CLEANING
Figure 3: Typical filter emissions
INCREASED SPIKE AND
BASELINE BECAUSE
OF FILTER WEAR
REPLACED
FILTERS
TIME