An Instrument is a measurement or sensing device on a P&ID drawing. Instruments represent transmitters, indicators, controllers, and other measurement equipment. Unlike Engineering Items, instruments do not directly control fluid flow — instead, they monitor process variables and provide data for conditions.
In pharmaceutical manufacturing, instruments are critical for verifying process parameters — confirming that SIP temperatures reach sterilization thresholds, that WFI conductivity stays within specification, and that tank pressures remain safe during CIP.
📋 Properties
|
Property |
Type |
Description |
|---|---|---|
|
Name |
Text |
Instrument tag/identifier (e.g., "TT-101", "FI-201", "PT-301") |
|
Phenomenon |
Text |
The physical phenomenon being measured (e.g., "Temperature", "Pressure", "Flow", "Level") |
|
Unit |
Text |
Measurement unit (e.g., "°C", "bar", "L/h", "mm") |
|
Instrument Type |
Text |
Classification (e.g., "Transmitter", "Indicator", "Controller", "Switch") |
|
Loop Number |
Text |
Instrumentation loop association |
|
Is Control Valve |
Boolean |
Whether this instrument is linked to a control valve |
|
FCE |
Reference |
Final Control Element — the Engineering Item this instrument controls |
|
Secondary Shapes |
List |
Related visual entities (tag text, annotations) |
|
Custom Attributes |
Collection |
User-defined attribute key-value pairs |
🎨 Instrument Coloring
Instruments are colored differently from Engineering Items. Instead of receiving state assignments, instruments are automatically colored based on how they are referenced in the Algorithm Design:
|
Coloring Context |
Meaning |
Visual Indicator |
|---|---|---|
|
Referenced in a Condition |
The instrument is used in a condition expression |
Highlighted when viewing condition logic |
|
Referenced in a Success Action |
The instrument is used in a success action |
Highlighted in success action context |
|
Referenced in a Fail Action |
The instrument is used in a fail action |
Highlighted in fail action context |
|
Referenced in a Prompt |
The instrument is used in a prompt text |
Highlighted in prompt context |
This coloring helps you quickly see which instruments are involved in the current step's control logic.
🔗 Control Valve Link
When an instrument has Is Control Valve enabled, it is linked to an Engineering Item as a Final Control Element (FCE). This establishes the relationship between the measurement device and the valve it controls.
The Loop Number typically matches between the instrument and its associated control valve, following standard instrumentation naming conventions (e.g., TIC-101 controls TV-101).
📐 Instrument in Algorithm Design
Instruments are used in conditions and actions:
-
In conditions — instrument readings are compared against Parameters (e.g., "TT-101 is greater than MaxTemp")
-
In actions — instrument readings can be recorded to Variables (e.g., "RecordedTemp equals TT-101")
-
In prompts — instrument values can be displayed in operator prompts
📌 Example: Common Instruments
|
Instrument |
Phenomenon |
Unit |
Type |
Loop |
|---|---|---|---|---|
|
TT-101 |
Temperature |
°C |
Transmitter |
101 |
|
PT-201 |
Pressure |
bar |
Transmitter |
201 |
|
FI-301 |
Flow |
L/h |
Indicator |
301 |
|
LT-401 |
Level |
mm |
Transmitter |
401 |
|
TIC-101 |
Temperature |
°C |
Controller |
101 |
💊 Pharma Scenario: Pressure Transmitter Monitoring Tank Pressure During SIP
During a Steam-In-Place (SIP) cycle on a process vessel, the pressure transmitter PT-201 plays a critical role:
|
SIP Phase |
PT-201 Reading |
Algorithm Usage |
What Happens |
|---|---|---|---|
|
Pre-heat |
0.2 bar |
Condition: PT-201 < SteamStartThreshold |
System waits until condensate is drained and pressure is low enough to begin steam injection |
|
Steam ramp-up |
0.8 bar |
Condition: PT-201 >= SterilizationPressure |
Steam injection continues until the vessel reaches the target sterilization pressure |
|
Hold |
1.0 bar |
Condition: PT-201 >= SterilizationPressure for HoldTime |
Pressure must remain above threshold for the entire hold duration |
|
Cool-down |
0.3 bar |
Condition: PT-201 < SafeOpenPressure |
Vessel pressure must drop below a safe level before outlet valves can open |
In the algorithm, PT-201 is referenced in the condition for each step. AseptSoft highlights PT-201 on the P&ID whenever you are viewing or editing these conditions, making it easy to trace control logic back to the physical instrument.
🛠️ How To: Use an Instrument in a Condition
-
Open the Algorithm Design for the desired step.
-
In the condition editor, select the instrument (e.g., PT-201) as the input source.
-
Choose the comparison operator and reference a Parameter (e.g., "SterilizationPressure").
-
The instrument is now highlighted on the P&ID when viewing this condition.
-
Repeat for success/fail actions if the instrument reading should be recorded or displayed.
🔗 Related Pages
-
Engineering Item — Control valves linked to instruments
-
Source — Fluid origin points that instruments may monitor
-
Parameter — Values instruments are compared against in conditions
-
Control Loop — PID loops that reference instruments
-
Algorithm Design — Where instruments are used in conditions
-
PID Shape Components — All shape component types
-
P&ID Components Classification — How instruments are classified