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pH 4.00 Calibration Solution — Atlas Scientific
The Atlas Scientific pH 4.00 Calibration Solution is a precision reference liquid used to calibrate pH sensors and EZO™ pH circuits. Accurate calibration is the foundation of reliable pH measurement — without it, your sensor readings will drift and become untrustworthy over time.
This solution is manufactured to strict NIST-traceable standards, ensuring the pH value is accurate and consistent from bottle to bottle. It's essential for anyone doing serious water quality monitoring, hydroponics, aquaculture, aquarium management, or environmental sensing.
Calibration tip: For best accuracy, perform a 3-point calibration using all three solutions:
pH 4.00 (acid),
pH 7.00 (neutral), and
pH 10.00 (base).
A 2-point calibration (pH 4 + pH 7, or pH 7 + pH 10) is acceptable for narrower measurement ranges.
Why calibration matters
- Sensor drift: pH probes naturally drift over days and weeks — regular calibration corrects this
- Temperature effects: pH readings shift with temperature; calibration at your working temperature improves accuracy
- Probe aging: As probes age, their response curve changes — calibration compensates
- Trusted data: Uncalibrated sensors can be off by 0.5–2.0 pH units, which is significant in most applications
pH calibration point guide
| Solution | pH Value | Type | When to use |
|---|---|---|---|
| pH 4.00 | 4.00 | Acidic | Calibrating for acidic measurements (pools, fermentation, soil) |
| pH 7.00 | 7.00 | Neutral | Always use — the baseline midpoint for all calibrations |
| pH 10.00 | 10.00 | Basic/Alkaline | Calibrating for alkaline measurements (aquariums, wastewater) |
Compatible Atlas Scientific products
Designed for use with Atlas Scientific pH probes and the EZO™ pH Circuit. Also works with any standard pH sensor or meter that requires buffer solution calibration.
What you can monitor
Hydroponics nutrient solutions, aquarium and reef tank water, swimming pool chemistry, drinking water quality, wastewater treatment, soil pH, fermentation processes, and laboratory experiments.
Technical specifications
| Product | Atlas Scientific pH 4.00 Calibration Solution |
|---|---|
| pH Value | 4.00 (±0.01 at 25°C) |
| Type | Acidic buffer |
| Traceability | NIST-traceable |
| Format | Liquid solution (bottle) |
| Shelf life | Use within expiry date printed on bottle; store sealed at room temperature |
Storage & handling
Keep bottles sealed and stored at room temperature away from direct sunlight. Do not pour used solution back into the bottle — always use a clean sample to avoid contamination. Discard solution after use.
Frequently Asked Questions
How often should I calibrate my pH sensor?
For critical applications, calibrate weekly. For general monitoring, monthly calibration is usually sufficient.
Always recalibrate after replacing a probe or if readings seem inconsistent.
Do I need all three solutions?
A 2-point calibration (pH 7 + one other) is fine for most uses. 3-point calibration provides the best accuracy
across the full pH range. Always include pH 7.00 as your midpoint.
Can I use this with non-Atlas Scientific sensors?
Yes. Standard pH buffer solutions work with any pH probe or meter that requires calibration.
Does temperature affect calibration?
Yes. Calibrate at the same temperature you'll be measuring at for best accuracy. Most EZO circuits include
automatic temperature compensation when paired with a temperature sensor.
Manila stock. Order before 16:00 PHT, ships today via J&T or LBC. Provincial: 1–3 working days.
Schools / class POs: we accept Purchase Orders for accredited schools and universities. contact us with your PO details.
Returns: 7-day inspection window for DOA units. Email proof of issue and we ship a replacement.
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