3) Thermowell Details a: material, b: Construction, c: dimension, e: connection. Temperature Element. We have collect following information to prepare D/s.ġ) Type of Temperature Sensor(T/C or RTD, in case of T/c which type J,K,R,S etc.)Ģ) Head details a: Screw-cap and chain, b: material, c: conduit connections, d: terminal block> single or duplex.

While making Datasheets which things are to be considered?īasically it depends on the instrument item for which you are preparing the datasheet. 7) According to the Cause and effects diagrams the System programmer assigns the control action block into the system, we can call them as memory assigning. 6) For both the system Marshalling panels, Consoles and other faculties of Ethernet Etc can be used according to the need.

6) DCS & PLC’s speed depends on the scan rate of I/Os. Some of the time it is used to handle few nos of AI/AO. 5) As I heard the PLC used to handle the DI/DO signals so it can take fast actions. 4) In the above mentioned case the these PLC’s can be get connected with the DCS with the help of soft link. Generally this is used to make alert to both the operator. Where as PLC has own limitations so it generally used for small but for important(Safety point of view) units, like boiler automations, Make-up compressor automations Etc. 3) DCS can handles handsome quantity of I/Os so that can be used for total plant automation. Basic difference between DCS & PLC is 1) DCS handles more nos of I/Os rather than PLC. These are the control systems which handles fields I/Os. control action and that given to the final control element as per the process requirement.ĭistributed control system(DCS) and Programmable logic controller. Means Tx sense the process and send it to the control room. OPEN LOOP : This is nothing but to sense the process signals from the field and to send it to the control room for operator observation.ĬLOSE LOOP : This is measuring the process signals for operator’s action. Because digital outputs are powered signal, by wrong connection there may be chances to damage the card.įor DCS I/p & o/p and PLC I/p & o/p we used separate JB’s. Instrument JB’s depend upon hazards area classification.įor IS signal IS JB’s used for NIS signal NIS JB’s usedįor analog I/p & o/p signal we can use same JB.īut for Digital I/p & o/p we have to use separate JB’s. Which cable to use, depends upon hazards condition. IS – Intrinsic safety & NIS – Non Intrinsic safety Limit switch, press,temp,flow,level switch) are digital input to control system.Īll powered signals (24V,48V,110V….) from system to instruments (SOV) are Digital outputs. Volt free (24V) contact (NO/NC) by instruments (all type of switches, ex. What are Analog Input/output & Digital Input/output?Ĥ-20 mA signals from instrument (transmitters) are analog input to control system.Ĥ-20 mA signals to instrument (I/p & electro pneumatic positioner) are analog output from control system.

Instrumentation interview questions