### **Must Read Before Buying: What Signal Types Does the PR235 Support? A Complete Guide**

For instrumentation engineers, maintenance technicians, and procurement specialists, selecting the right calibrator hinges on one critical question: "Can it handle all the instruments on my loop sheet?" A device that falls short in signal coverage becomes a costly liability, forcing you to purchase additional tools and complicating your workflow.

The PR235 Multifunction Process Calibrator is designed to be a comprehensive solution. This article provides a definitive, in-depth analysis of every signal type the PR235 supports, translating technical specifications into real-world application to help you confirm it's the right tool for your plant.

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#### **Core Capability 1: Pressure Measurement and Sourcing**

The PR235 is, at its heart, a highly accurate pressure calibrator. Its capabilities here are often the primary reason for its selection.

*   **Supported Types:**

    *   **Gauge Pressure (PSIG, kPaG, barG, etc.):** The most common type for process applications. The PR235 can both generate (source) and measure pressure relative to atmospheric pressure.

    *   **Absolute Pressure (PSIA, kPaA, barA):** Critical for applications like vacuum distillation, evaporators, and barometric pressure reference. The PR235 references a sealed vacuum zero point.

    *   **Differential Pressure (inH2O, mmHg, etc.):** Essential for flow measurement (across orifice plates) and level measurement in closed tanks. The PR235 can apply and measure a pressure difference between its two ports.

    *   **Vacuum (inHg, mmHg):** The ability to generate and pull a vacuum is key for testing vacuum switches, transmitters, and gauges.

*   **Key Specifications to Check:**

    *   **Pressure Range:** The PR235 is available in multiple models with different maximum pressure ranges (e.g., 300 psi, 1000 psi, 3000 psi). You must select the model that exceeds the maximum pressure you need to calibrate.

    *   **Accuracy:** Typically around ±0.05% of full scale for high-end models, which is sufficient for a 4:1 TUR on most industrial pressure instruments.

    *   **Integrated Pump:** Features a built-in, precision hand pump for generating pressure, eliminating the need for a separate, cumbersome tool.

#### **Core Capability 2: Electrical Measurement and Sourcing**

This is where the PR235 truly becomes "multifunction," replacing a high-end digital multimeter (DMM) and a loop calibrator.

*   **Supported Types:**

    *   **DC Current (mA):** The lifeblood of process control (the 4-20mA signal). The PR235 can **measure** mA (to read an output) and **source/simulate** mA (to test a PLC input or chart recorder). This is its most-used electrical function.

    *   **DC Voltage (V/mV):** Used for various sensor outputs (0-5V, 0-10V, 1-5V) and testing I/O modules. It supports both measuring and sourcing voltage.

    *   **Resistance (Ω):** Used for testing and simulating RTD sensors (e.g., Pt100) and potentiometers. The PR235 can source a precise resistance value to test a temperature transmitter or measure the resistance of an RTD.

    *   **Frequency (Hz):** Used for testing turbine flow meters, vortex meters, and other frequency-output devices. The PR235 can both measure an incoming frequency and generate (source) a precise frequency signal.

    *   **Voltage (Thermocouple mV):** While not a direct TC simulator, it can measure the millivolt output from a thermocouple and, crucially, use its **HART function** to read the temperature value from a connected temperature transmitter.

#### **Core Capability 3: Temperature Simulation and Measurement (with Transmitters)**

It is vital to understand that the PR235 is **not a temperature source** like a dry-block furnace. Instead, it handles temperature by simulating and measuring the electrical signals that represent temperature.

*   **How it Works:**

    *   **Simulating a Sensor:** You can tell the PR235 to output the exact resistance (for an RTD like Pt100) or millivoltage (for a Thermocouple Type J, K, T, etc.) that corresponds to a specific temperature. This is injected into a temperature transmitter to test its calibration and response.

    *   **Measuring a Sensor Output:** You can connect an RTD or thermocouple directly to the PR235's electrical terminals to measure its output and determine the temperature it is sensing (though for high-accuracy sensor calibration, a dry-block is still required to provide the actual temperature source).

#### **Core Capability 4: Communication Protocols (The "Smart" Function)**

This is the feature that separates a modern calibrator from a simple signal generator. The PR235 can communicate with intelligent field devices.

*   **Supported Protocol:**

    *   **HART (Highway Addressable Remote Transducer):** The universal standard for smart analog instruments. The PR235 has a full HART modem integrated. This allows it to:

        *   **Read Digital PV:** See the temperature/pressure value the smart transmitter is calculating, even while also measuring the 4-20mA analog signal.

        *   **Configure Devices:** Change ranges (re-range), set damping values, adjust LRV/URV, and perform sensor trim (calibration) procedures.

        *   **Diagnose Problems:** Read device status, alerts, and configuration information to troubleshoot issues.

#### **Practical Application Scenarios**

To put this into context, here’s what the PR235 can do on a single job:

1.  **Calibrate a Pressure Transmitter:** Use the pump to apply pressure, measure the 4-20mA output, and use HART to read the digital value and trim the sensor.

2.  **Troubleshoot a Temperature Loop:** Simulate a Pt100 resistance into the temperature transmitter and measure its 4-20mA output to isolate a fault to the sensor or the transmitter.

3.  **Verify a PLC Analog Input Card:** Source a precise 4-20mA or 1-5V signal to test every channel on the card.

4.  **Test a Flow Meter:** Generate a frequency signal to simulate flow and verify the receiving system reads it correctly.

#### **What It Does NOT Do**

For clarity, be aware of these limitations:

*   **It is not a standalone temperature calibrator.** It requires a separate dry-block furnace to provide a known temperature source for calibrating RTD and thermocouple sensors themselves.

*   **It does not support Fieldbus protocols** like Foundation Fieldbus H1 or PROFIBUS PA. These require dedicated communicators.

#### **Conclusion: The Ultimate Field Toolkit in One Device**

The PR235's supported signal list covers over 95% of the calibration and troubleshooting tasks for analog and HART-enabled instruments in a typical process plant. By supporting **pressure, electrical (mA, V, Ω, Hz), temperature simulation (RTD/TC), and HART communication**, it consolidates your toolkit, reduces errors, and drastically improves field efficiency.

Before purchasing, simply cross-reference this list against your instrument inventory. You will likely find that the PR235 isn't just a supported device; it's the central hub for your entire calibration program.