How to Calibrate the Ohaus PX224/E Pioneer Analytical Balance

Accurate calibration is essential for achieving reliable weighing results with an analytical balance. The Ohaus PX224/E Pioneer Analytical Balance is designed for high-precision laboratory applications and uses external calibration (ExCal) to maintain measurement accuracy.

This guide explains how to properly calibrate the Ohaus PX224/E using certified external weights, following the official procedures outlined in the Ohaus PX Series Instruction Manual, rewritten in a clear, user-friendly, and SEO-optimized format.

Understanding Calibration on the Ohaus PX224/E

The PX224/E is classified as an ExCal analytical balance, which means:

• It does not contain an internal calibration weight

• Calibration must be performed using external certified calibration masses

• The balance supports:

  • Span Calibration

  • Linearity Calibration

According to Ohaus, calibration should be performed:

• During initial installation

• After relocating the balance

• When ambient conditions change

• As part of routine quality control or compliance programs

Pre-Calibration Checklist (Critical for Accuracy)

Before beginning calibration, ensure the following conditions are met:

1. Warm-Up and Acclimatization

• Allow the balance to warm up for at least 1.5 hours

• Analytical balances require sufficient time to stabilize thermally

2. Proper Environment

• Place the balance on a stable, vibration-free surface

• Avoid drafts, fans, air conditioning vents, and direct sunlight

3. Level the Balance

• Adjust the leveling feet until the bubble indicator is centered

4. Use the Correct Calibration Weights

For the Ohaus PX224/E, the official calibration values are:

• 100 g

• 200 g (full capacity)

Use ASTM Class 1 or equivalent certified calibration weights for best accuracy.

How to Perform Span Calibration on the PX224/E

Span calibration adjusts the balance using a zero point and a known reference weight.

Step-by-Step Span Calibration Instructions

1. Turn the Balance ON

   • Ensure the weighing pan is empty

2. Enter the Calibration Menu

   • Press and hold the Tare / Menu-Cal button

3. Select Span Calibration

   • Press Yes to enter the Calibration menu

   • Press No until Span Cal appears

   • Press Yes to confirm

4. Apply the Calibration Weight

   • The display will show “Place weights”

   • Place the displayed calibration mass (typically 200 g) on the pan

   • To use the half-capacity point (100 g), press the Function / Mode button

5. Confirm Calibration

   • The balance automatically captures the value

6. Remove the Weight

   • Follow the on-screen prompt to remove the calibration mass

7. Completion

   • The display will show “Calibration done”

   • Press any key to return to normal weighing mode

How to Perform Linearity Calibration(Recommended)

Linearity calibration improves accuracy across the entire weighing range, not just at one point.

When Linearity Calibration Is Recommended

• Regulated or validated laboratory environments

• After transport or relocation

• If results vary at different weight levels

Linearity Calibration Overview

1. Enter the Calibration Menu

2. Select Linearity Cal

3. Follow on-screen prompts to apply:

   • Zero load

   • 100 g

   • 200 g

4. When complete, the display will show “Linearity done”

Best Practices for Analytical Balance Calibration

• Use clean, temperature-stable calibration weights

• Never touch weights with bare hands

• Calibrate daily or weekly, depending on usage

• Keep calibration records for GLP, ISO, GMP, or USP compliance

• Re-calibrate after environmental or location changes

When to Use Professional Calibration Services

Professional calibration is recommended when:

• The balance is used for ISO, GLP, GMP, or USP-regulated work

• NIST-traceable calibration certificates are required

• The balance fails internal performance or verification checks

Authorized calibration providers can verify performance and document compliance.

Final Thoughts

Proper calibration of the Ohaus PX224/E Pioneer Analytical Balance ensures dependable weighing results, regulatory compliance, and long-term instrument performance. By following Ohaus-approved procedures and maintaining proper environmental conditions, laboratories can achieve consistent and highly accurate measurements.