Quick verdict
Eight ounces of conductivity standard made in an ISO 17025 certified US laboratory to 1413 microsiemens per centimetre at 25 C, accurate to 5, for calibrating the EC, TDS and salinity meters used on soil, hydroponic reservoirs and irrigation water. A meter that has never been calibrated reads a number; a meter calibrated against a known standard reads the truth. Apera is a meter maker and its solutions suit any brand. Use fresh solution each time and keep the bottle sealed.
Strengths
- Lab-certified 1413 µS/cm standard, accurate to 5
- Calibrates EC, TDS and salinity meters of any brand
- Eight ounces is many calibrations
- Made in the USA in an ISO 17025 lab
- Reveals whether a cheap meter can be trusted
Weaknesses
- Must be used fresh; a poured-out portion is single use
- Needs temperature compensation or a reading at 25 C
- Only one point; meters with two-point calibration want a second standard
The overall YardToolLab Score is out of 100. Section scores are out of 10.
A Meter Is Only as Good as Its Calibration
An EC meter for soil salinity or a hydroponic reservoir gives a number every time, and without calibration nobody knows whether the number is right. A conductivity standard is the reference. Apera’s is made in an ISO 17025 certified US laboratory to 1413 microsiemens per centimetre at 25 C, accurate to 5, in an 8 ounce bottle that covers months of calibrations for any brand of meter.
This review is based on the maker’s specifications and on standard practice for conductivity meter calibration. We have not used this solution ourselves.
The Standard
1413 µS/cm is the universal single-point standard for conductivity, made from a precise potassium chloride solution. A meter reading it should show 1413 at 25 C, or the equivalent TDS figure, and if it does not, the calibration function corrects it. Lab certification is the difference between a standard and a bottle of salty water.
Calibrating
Pour a little into a clean cup, rinse the probe in it and discard that portion. Pour fresh, immerse the probe to its mark and wait for the reading to settle with temperature compensation on or the solution at 25 C. Set the meter to 1413 according to its manual. Discard the used solution; never pour it back, since the probe carries contamination in. Cap the bottle tightly between uses.
What It Reveals
A quality meter reads within a percent or two and holds it for a month. A cheap meter may read 20 percent off and drift weekly, which is useful to know before trusting it on a crop. Calibrating is also when a fouled probe is noticed and cleaned.
Frequency
Monthly in regular use, before any reading that matters, and after the probe is cleaned or the meter dropped. Eight ounces at a capful or two a time is many months.
Who Should Buy It
- Anyone with an EC, TDS or salinity meter for soil or hydroponics.
- Greenhouse growers managing feed strength.
- Owners of budget meters who want to know how far off they are.
Common Owner Complaints
Solution used from the bottle directly and contaminated. Pour out, use, discard.
Technique Tips
Let the solution and the probe sit in the same room for half an hour so both are at the same temperature before calibrating. Use a clean plastic cup rather than glass, which can hold residues, and rinse the probe in distilled water between the standard and the sample. Write the calibration date on tape on the meter. If the meter needs a large correction twice in a row, the probe is fouled or failing.
Alternatives to Consider
A 12880 µS/cm standard for a second high point on two-point meters. Single-use calibration sachets for occasional users. Hanna and Bluelab standards for their meters.
Verdict
For any EC meter, a certified standard is what makes the readings trustworthy, and this bottle is accurate, economical and brand-neutral. Calibrate monthly with fresh solution and the numbers mean something.
Full specifications
Apera Instruments 1413 µS/cm Conductivity Standard Calibration Solution, 8 oz, Lab Certified FAQs
Probes drift as they age and foul. A standard of known conductivity shows the error and lets the meter be adjusted, so readings of soil salinity or nutrient strength mean something.
Pour a little into a clean cup, rinse the probe in it, discard, pour fresh and immerse the probe. Wait for a stable reading at 25 C or with compensation on, then set the meter to 1413 per its instructions. Never return solution to the bottle.
Monthly in regular use, before any important reading, and whenever the meter is dropped or the probe cleaned.
Yes. TDS is EC converted; 1413 µS/cm reads as about 707 ppm on a 0.5 factor meter or 1000 on a 0.7 factor. The meter instructions give the figure.
