Instrumentation, Measurement and Control - Ashcroft
Instrumentation refers to devices that measure or control physical variables such as temperature, level, flow, or pressure. These products are essential in the industry because they allow for maximum output with mi...
Process pressure gauges are built for chemical, petrochemical, refining and power plant service. Heavy-duty cases, stainless wetted parts and high accuracy give dependable readings in demanding environments.
Process Gauge Features
- Solid-front safety cases – operator protection
- 316 stainless steel internals – corrosive media
- Liquid filling – vibration and pulsation damping
- Accuracy to 0.5% – precise readings
- 4.5" and 6" dials – easy reading
Choosing a Process Gauge
Choose range, accuracy, connection and materials suited to the process. Add diaphragm seals for corrosive, viscous or high-temperature media.
Centro supplies process gauges and accessories for plant instrumentation.
Related categories: Pressure Gauges | Commercial Gauges | Industrial Gauges | Test Gauges | Differential Pressure Gauges
Pressure switches open or close an electrical contact when pressure reaches a set point. They start and stop pumps and compressors, trigger alarms and shut equipment down when pressure is unsafe.
Pressure Switch Types
- Mechanical switches – simple, reliable and no power needed
- Electronic switches – adjustable set points and displays
- Differential pressure switches – filter and flow monitoring
- Vacuum switches – vacuum system control
- Explosion-proof switches – hazardous areas
Choosing a Switch
Select set point range, deadband, electrical rating and wetted materials. Fixed or adjustable deadband affects cycling. Add snubbers for pulsating systems.
Centro carries pressure switches for pumps, compressors and process safety.
Related categories: Pressure Control | Pressure Transmitters | Gauges | Pressure Regulators | Pressure Control Accessories
Industrial pressure gauges are built for the vibration, pulsation and rough handling found in plants, pump rooms and machinery. They give operators a dependable local reading of pressure in water, air, oil, steam and process lines.
Industrial Gauge Options
- Stainless steel cases – corrosion resistance and durability
- Liquid-filled gauges – dampen vibration and pulsation for steady readings
- Brass and stainless internals – match media compatibility
- Bottom and back connections – for line and panel mounting
- Dial sizes from 2" to 6" – readable at a distance
Selecting a Gauge
Choose a range so normal operating pressure sits in the middle of the dial, generally about twice the operating pressure. Use a liquid-filled gauge on pumps and compressors, and add a snubber for pressure spikes. Confirm the connection size and accuracy grade.
Centro carries industrial pressure gauges for plant, process and equipment applications.
Related categories: Pressure Gauges | Process Gauges | Commercial Gauges | Test Gauges | Differential Pressure Gauges
Bimetal thermometers are widely used temperature measurement devices that employ a bimetallic strip to indicate temperature changes. These thermometers consist of two metal strips, typically made of different metals with different coefficients of thermal expansion, bonded together. The metals expand or contract at different rates as the temperature changes, causing the bimetallic strip to bend. This bending motion is then translated into a rotational movement displayed on a calibrated dial to indicate the temperature. Bimetal thermometers are known for their simplicity, durability, and cost-effectiveness. They are commonly used in various industries and applications requiring reliable temperature monitoring, such as HVAC systems, automotive, food processing, and industrial processes. Bimetal thermometers offer advantages such as wide temperature ranges, resistance to shock and vibration, and ease of installation. They are available in different sizes and configurations to suit specific application requirements. With their robust construction and accurate temperature indication, bimetal thermometers provide a reliable and cost-effective temperature measurement solution in various industrial and commercial settings.
Related categories: Thermometers | Industrial Thermometers
Temperature switches open or close a contact at a set temperature to start fans, stop heaters, trigger alarms or shut down equipment. They're simple, dependable temperature protection.
Switch Types
- Mechanical switches – bulb and capillary or bimetal
- Electronic switches – adjustable set points and displays
- Limit switches – high-limit safety shutoff
- Explosion-proof switches – hazardous areas
Choosing a Switch
Select range, deadband, contact rating and sensor style. Use thermowells for pressurized systems. Manual-reset limits add safety.
Centro supplies temperature switches for equipment protection and control.
Related categories: Temperature Measurement, Instrumentation and Control | Temperature Controllers | Thermocouples and RTDs | Temperature Recording | Thermometers
Pressure transducers convert pressure into an electrical signal for PLCs, data loggers and controls. They provide continuous monitoring of hydraulics, pneumatics, water systems, HVAC and process equipment.
Transducer Options
- Output types – millivolt, 0-5 V, 0-10 V, 4-20 mA and digital
- Gauge, absolute and sealed references – suited to the measurement
- Stainless steel wetted parts – compatible with most media
- Compact OEM transducers – high-volume machine builds
- Hazardous area models – intrinsically safe and explosion-proof
Choosing a Transducer
Select a range so normal pressure sits around 50-75% of full scale, and consider accuracy, temperature effects and overpressure ratings. Protect against pressure spikes with snubbers. Match connectors and cable to the installation.
Centro carries pressure transducers for industrial, mobile and process applications.
Related categories: Pressure Control | Pressure Control Accessories | Gauges | Pressure Switch | Pressure Transmitters
Pressure transmitters send accurate pressure readings to your control system over long distances. They're the standard instrument for process monitoring, control loops and safety systems.
Transmitter Types
- Gauge and absolute transmitters – line pressure measurement
- Differential pressure transmitters – flow, level and filter monitoring
- Smart transmitters – HART and digital communication
- Remote seal transmitters – hot, viscous or corrosive media
- Hazardous area models – explosion-proof and intrinsically safe
Choosing a Transmitter
Select range, accuracy, process connection and wetted materials. Consider output, display and approvals. Manifolds simplify installation and calibration.
Centro supplies pressure transmitters and manifolds for process measurement.
Related categories: Pressure Control | Pressure Regulators | Pressure Switch | Sequence Valves | Gauges
Commercial pressure gauges cover HVAC, plumbing, fire protection and general building services. They're economical, easy to read and available in many standard ranges.
Commercial Gauge Options
- Dry and liquid-filled gauges – general service
- Brass internals – water, air and oil
- Common dial sizes – 2" to 4"
- Bottom and back connections – line or panel mounting
- Fire protection gauges – sprinkler system ratings
Choosing a Gauge
Select a range about twice normal operating pressure, and match connection size and dial type. Liquid-filled gauges handle vibration from pumps.
Centro supplies commercial gauges for HVAC, plumbing and building systems.
Related categories: Pressure Gauges | Test Gauges | Process Gauges | Differential Pressure Gauges | Industrial Gauges
Pressure control accessories protect instruments, simplify maintenance and make pressure measurements more accurate. Syphons, snubbers, manifolds and valves are essential to a dependable gauge or transmitter installation.
Accessories Available
- Pressure snubbers – dampen pulsation and spikes
- Syphons – protect gauges from live steam
- Manifold valves – isolate and equalize transmitters
- Gauge cock and instrument valves – isolate instruments for service
- PT plugs – quick test ports for pressure and temperature checks
Building an Installation
A typical gauge installation includes an isolation valve, a protection device (snubber or syphon) and the gauge itself. Choose materials compatible with the media and pressure ratings above system maximum.
Centro carries pressure control accessories to complete and protect your instrument installations.
Shop by type: Pressure Snubber | Manifold Valves | Gauge Cock Valve | Instrument Valve | Syphons | Instrument Valve Accessories | PT Plugs
Related categories: Pressure Control | Gauges | Pressure Transducers | Pressure Switch | Pressure Transmitters
Test gauges, also called calibration gauges, provide high-accuracy readings for checking and calibrating other instruments. They're essential tools for maintenance and instrument technicians.
Test Gauge Options
- Analog test gauges – 0.25% accuracy with mirror dials
- Digital test gauges – high accuracy and data logging
- Wide range selections – vacuum to high pressure
- Calibration certificates – traceable documentation
Choosing a Test Gauge
Select accuracy at least four times better than the instruments you're testing. Choose range and connection to match. Handle and store test gauges carefully to protect accuracy.
Centro supplies test gauges for calibration and verification.
Related categories: Pressure Gauges | Differential Pressure Gauges | Commercial Gauges | Digital Gauges | Process Gauges
Diaphragm seals are devices that seal pressure transmitters to prevent process fluid from coming into contact with the inner workings of the transmitter. Our diaphragm seals are made from high-quality rubber resistant to wear and tear. They are available in various sizes to fit most pressure transmitters. Centro supplies threaded, flanged, sanitary and in-line diaphragm seals, and can help you choose the right seal and fill fluid for your gauge or transmitter. In addition, we offer a wide range of accessories for diaphragm seals, including replacement diaphragms, o-rings, and mounting brackets. Whether you need a single diaphragm seal or a complete Diaphragm Seal kit, we have the products to keep your pressure transmitter working correctly.
Related categories: Seals | Capillaries | Seal Accessories | Isolation Rings | O-Rings
Thermowells protect temperature sensors from pressure, flow, corrosion and abrasion. They also let you remove sensors for replacement or calibration without draining or shutting down the process.
Thermowell Types
- Threaded thermowells – common for general service
- Socket weld and weld-in – high-pressure installations
- Flanged thermowells – easy removal and corrosive service
- Sanitary thermowells – tri-clamp for food and pharma
- Tapered and stepped stems – strength and fast response
Choosing a Thermowell
Select material, insertion length, bore size and connection. For high-velocity flows, perform a wake frequency calculation to avoid stem failure.
Centro supplies thermowells for temperature sensors and thermometers.
Related categories: Temperature Measurement, Instrumentation and Control | Temperature Regulators | Temperature Transmitters | Temperature Sensors | Temperature Recording
Diaphragm seals protect pressure gauges, switches and transmitters from corrosive, viscous, hot or clogging process media. A flexible diaphragm transfers pressure through a fill fluid so the instrument never touches the process.
Diaphragm Seal Types
- Threaded seals – general-purpose protection
- Flanged seals – larger connections and higher pressures
- Sanitary seals – tri-clamp for food and pharma
- In-line seals – slurries and flowing media
- Capillary systems – remote mounting
Choosing a Seal
Select diaphragm material, fill fluid and connection for your process. Consider temperature effects and instrument range. Assemblies are often filled and calibrated as a unit.
Centro supplies diaphragm seals and can help you choose the right seal and fill fluid for your instrument.
Related categories: Seals and Accessories | Capillaries
Temperature accessories help your sensors and instruments read accurately and last longer. Thermowells, fittings, connection heads and extension wire protect sensors from the process and make installation and replacement simpler.
Accessories Available
- Thermowells – threaded, socket weld and flanged wells protect sensors from pressure and flow
- Compression fittings – adjustable sensor insertion depth
- Connection heads – house terminal blocks and head-mount transmitters
- Thermocouple and RTD extension wire – carry signals back to the controller
- Connectors and plugs – quick disconnects for sensors
Choosing Accessories
Select thermowell material and length for the process, with the tip in the flow, and check the wake frequency calculation for high-velocity lines. Use extension wire that matches the thermocouple type to avoid reading errors. Head and enclosure ratings should match the environment.
Centro carries temperature accessories to complete your sensor installations.
Related categories: Temperature Measurement, Instrumentation and Control | Thermometers | Heat Exchangers | Thermocouples and RTDs | Temperature Switches
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- Selecting the right process instrument starts with defining four things: what variable you need to measure (temperature, pressure, flow, or level), the process conditions the instrument will face (media type, temperature range, pressure range, corrosiveness, and whether the environment is hazardous), the accuracy and response time your application requires, and how the measurement data needs to be communicated (local display only, 4–20 mA signal to a PLC/DCS, or digital protocol like HART or Modbus). For temperature, the choice between thermocouples, RTDs, and infrared sensors depends on the temperature range and accuracy needed. For pressure, gauge type, range, wetted materials, and whether you need local indication or a remote transmitter signal are the key decisions. For flow, the fluid properties (conductive liquid, gas, steam, slurry) determine whether a magnetic, ultrasonic, Coriolis, vortex, or variable-area meter is the best fit. For level, vessel conditions (open vs. pressurized, clean liquid vs. foam/solids) guide the choice between float switches, ultrasonic, radar, or differential pressure technologies. Centro's instrumentation specialists can help you match the right technology to your specific process conditions and budget.
- Accurate process instrumentation is the foundation of safe, efficient, and compliant operations. Every control loop — whether it manages boiler pressure, reactor temperature, tank level, or pipeline flow — depends on instruments that provide reliable, real-time measurements. If a temperature sensor reads inaccurately, a heater may overshoot and damage the product or create a safety hazard. If a level transmitter drifts, a tank may overflow or run dry. If a flow meter is undersized, the control system cannot maintain the correct feed rate. Beyond safety and quality, accurate instrumentation directly impacts energy consumption, raw material usage, and regulatory compliance. Calibrated, properly specified instruments reduce waste, prevent unplanned shutdowns, and provide the data required for regulatory reporting and quality documentation.
- A process control loop is a system that continuously measures a process variable, compares it to a desired setpoint, and adjusts an output to keep the variable at the setpoint. The loop consists of three elements: the sensor/transmitter (measures the variable — e.g., a thermocouple measuring temperature), the controller (compares the measurement to the setpoint and calculates a corrective output — typically a PID controller), and the final control element (adjusts the process — e.g., a control valve that opens or closes to change steam flow). Instruments are the eyes and ears of the loop — without accurate, responsive sensors and transmitters, the controller cannot make correct decisions, and the process drifts out of specification. The entire loop must be properly engineered as a system — sensor accuracy, transmitter range, controller tuning, and valve sizing must all be matched to the process requirements.
- Industrial instruments communicate with controllers and PLCs using standardized electrical signals. The 4–20 mA analog current loop is the most widely used signal in process instrumentation — it transmits a variable measurement as a proportional current (4 mA = zero/low range, 20 mA = full scale), and the current-based signal is resistant to voltage drop and electrical noise over long cable runs. The 0–10 V DC voltage signal is used in some HVAC and building automation applications but is more susceptible to noise and cable length limitations. Discrete (on/off) signals — from switches, relays, and transmitter alarm contacts — indicate threshold conditions like high level, low pressure, or flow/no-flow. Digital communication protocols — HART (layered on top of 4–20 mA for configuration and diagnostics), Foundation Fieldbus, PROFIBUS PA, and IO-Link — enable bidirectional communication between the instrument and the control system for advanced diagnostics, remote configuration, and multi-variable data.
- When instruments are installed in locations classified as hazardous (areas where flammable gases, vapors, or combustible dusts may be present), they must be approved for that classification to prevent ignition. Key considerations include the area classification (Class I for gases/vapors, Class II for dusts, with Division 1 for normally present hazards and Division 2 for abnormal conditions — or Zone 0/1/2 under ATEX/IECEx), the protection method (intrinsic safety, explosion-proof, non-incendive, or purged/pressurized), and the specific gas group and temperature class. Intrinsically safe (IS) instruments — used with IS barriers in the safe area — limit energy to levels too low to cause ignition and are the most common and practical approach for low-power sensors and transmitters. Explosion-proof enclosures contain any internal explosion and are used for higher-power devices. Always verify the instrument's certification (FM, CSA, ATEX, IECEx) matches the area classification before installation.