Operation; Normal Operation - Macurco Modbus RS-485 User Instructions

Power Up
The Macurco 6-Series detector cycles through an internal self-test cycle for the first minute that it is powered. The unit will execute
the test cycle any time power is dropped and reapplied (i.e. power failure). During the self-test cycle the unit will display the firmware
version number, then count down from 60 to 0 (if the display setting is "On") and finally go into normal operation. The alarm relay will
be activated for 10 seconds and the fan relay for 60 seconds during the power-up cycle unless the "Power Up Test" (PUt) option is
OFF. The indicator light (LED) will flash green during the self-test cycle. At the end of the 1 minute cycle, the unit will take its first
sample of the air and the indicator light will turn solid green.
The MRS-485 is an adapter which allows the reading of a 6-Series gas detector over a Modbus interface. To achieve this, the MRS-
485 will monitor the 4-20 mA current output of the detector. At power up and during its warm-up period, the 6-Series detector will
communicate its sensor type over the 4-20 current output using a custom protocol. The MRS-485 will automatically register each 6-
Series detector as it is programmed with information about all the detectors to which it can be connected. The MRS-485 will use this
information to determine the gas level sensed by the 6-Series detector by measuring the 4-20 mA current-loop output during normal
operation of the detector.
4-20mA Test Points
The MRS-485 has two Test Points labeled 1 and 2. These are provided to test the 4-20mA analog output directly from the detector,
using a meter and probes, without having to remove the MRS-485 from the detector. See the Testing section for more detail.

Operation

1. With the display function turned "On", the 6-Series detector will show the current concentration of gas or "0" (zero) in clean air.
When the gas concentration reaches the Fan Relay setting the display will flash back and forth between "FAn" and that
concentration. With the display function turned "Off", the display does not show the gas concentration, but will show "FAn" as
long as the fan relay is activated.
2. With the display function turned "On" and the gas concentration reaching the Alarm Relay setting, the display will flash back and
forth between "ALr" and that concentration. The buzzer will sound indicating "Alarm" if the buzzer is turned "On". With the
display function turned off the display does not show the gas concentration, but will show "ALr" when the Alarm relay is
activated.
3. With the 4-20 mA function turned "On" and the gas concentration climbing, the 4-20 mA signal will ramp up corresponding to the
concentration. The display will show "FAn" and "ALr" and sound as outlined above. The MRS-485 will monitor the 4-20 mA
current output of the detector. The MRS-485 has a Tricolor LED (RED, GREEN and AMBER) which is used to display the
status.

Normal Operation

1. When the LED is solid GREEN, operation is normal, the MRS-485 knows the detector type, no errors are detected and no
MODBUS data are being received or transmitted over the RS-485 line.
2. When the LED is GREEN with random bursts of AMBER, operation is normal and now data are being received or transmitted
over the RS-485 line. The AMBER LED will come on anytime that there is data traffic.