Langmuir Trough

This Langmuir trough is controlled with a Process Logic Controller M251 from Schneider. This PLC reads the analog signal returned by the surface tensiometer and drives the barriers through a Kibron electronics. The temperature of the liquid interface is controlled with a thermostatic bath and monitored with a compact pyrometer. A gas can be circulated above the interface via a flow-rate controller. In addition, the PLC controls the heating of the neutron and laser windows to prevent condensation. All these devices are controlled from the touch panel of the PLC which is also used to control the Adsorption Troughs.

Barriers are controlled manually with a touch panel or remotely with NOMAD. Their calibration is manual or semi-automatic and must be performed from the interface before closing the casemate. During neutron data acquisition, two modes of operation are proposed: area controlled and pressure controlled. In the pressure controlled mode, the movements of the barriers are determined by the Kibron electronics to maintain the wanted pressure (static or dynamic).

ModBus registers

Address	Access	Type	Description
40001	Read	Real	Surface tension signal x (V)
40003	Read	Real	Coefficient a
40005	Read	Real	Offset due to paper probe b
40007	Read	Real	Constant c for zeroing the sensor (relative measurement)
40009	Read	Real	Surface tension a x + b - c (mN/m)
40081	Read	Real	Temperature setpoint (°C)
40083	Read	Real	Temperature (°C)
40087	Read	Real	Gas flow rate (l/min)
40089	Read	Real	Gas flow rate setpoint (l/min)
40119	Read/Write	Real	NOMAD Control — Temperature setpoint (°C)
40121	Read/Write	Real	NOMAD Control — Gas flow rate setpoint (l/min)
40125	Read/Write	Real	NOMAD Control — Temperature tolerance (°C)
40127	Read/Write	Real	NOMAD Control — Gas flow rate tolerance (l/min)
40129	Read/Write	Integer	NOMAD Control — Year
40130	Read/Write	Integer	NOMAD Control — Month
40131	Read/Write	Integer	NOMAD Control — Date
40132	Read/Write	Integer	NOMAD Control — Hour
40133	Read/Write	Integer	NOMAD Control — Minute
40134	Read/Write	Integer	NOMAD Control — Second
40201	Read	Boolean (bit 0)	Temperature alarm (yellow: out of tolerance)
-	Read	Boolean (bit 2)	Temperature default (red)
-	Read	Boolean (bit 3)	Gas flow rate alarm (yellow: out of tolerance)
-	Read	Boolean (bit 5)	Gas flow rate default (red: out of gas)
-	Read	Boolean (bit 7)	Condensation default (red: lid unplugged)
40202	Read	Boolean (bit 0)	NOMAD Control — Thermostatic bath default (red: no communication)
-	Read	Boolean (bit 1)	NOMAD Control — Idle
-	Read	Boolean (bit 2)	NOMAD Control — Running
-	Read	Boolean (bit 3)	NOMAD Control — Local (0) / Remote (1)
-	Read/Write	Boolean (bit 4)	NOMAD Control — Default acknowledgment
-	Read/Write	Boolean (bit 5)	NOMAD Control — For resetting the PLC clock
40251	Read	Real	Voltage (mV) - Signal recieved by the KIBRON controller
40257	Read	Real	Area (mm2)
40277	Read	Real	Barriers Speed (mm/min)
40361	Write	Real	Manual Mode: Barriers Speed Setpoint (mm/min)
40351	Read/Write	Boolean (bit 0)	Manual mode: Compress
40352	Read/Write	Boolean (bit 0)	Manual mode: Relax
40353	Read/Write	Boolean (bit 0)	Manual mode: Stop
40367	Read/Write	Real	Area Controlled: Delay (min)
40373	Read/Write	Integer	Area Controlled: Number of Loops
40363	Read/Write	Real	Area Controlled: Barriers Speed Setpoint (mm/min)
40372	Read/Write	Real	Area Controlled: Target Area (mm2)
40354	Read/Write	Boolean (bit 0)	Area Controlled: Start (1)/Stop (0)
40371	Read/Write	Real	Pressure Controlled: Delay (min)
40375	Read/Write	Integer	Pressure Controlled: Number of Loops
40365	Read/Write	Real	Pressure Controlled: Barriers Speed Setpoint (mm/min)
40369	Read/Write	Real	Pressure Controlled: Target Surface Tension (mN/m)
40355	Read/Write	Boolean (bit 0)	Pressure Controlled: Start (1)/Stop (0)