If your Raven system shows a rate but the tank runs out early (or late), or the rate bounces for no obvious reason, the meter cal is the first thing to check. The number stamped on the flow meter tag is a factory starting point. Tags wear off, meters get swapped, and sensors get replaced with a different pulse type — any of which quietly changes the right number.
What the meter cal actually means
Raven meter cal is pulses per 10 gallons. A cal of 720 means 72 pulses per gallon. Lowering the meter cal decreases product output; raising it increases output. Raven flow meters put out a 5-volt square wave, so a voltmeter can't check the signal without the node connected — use the short/no-short test in our no-rate article for that.
Starting cals by meter (US / metric)
- RFM 5 — 5500 / 1455
- RFM 15 — 1750 / 493
- RFM 55 — 750 / 198
- RFM 60 P/S — 720 / 190
- RFM 100 — 700 / 185
- RFM 200 — 164 / 43
- RFM 400 — 80 / 21
- 3" Magmeter — 157 / 41
- 4" Magmeter — 100 / 26
- 6" Magmeter — 50 / 13
High-pulse sensors double the number. A "dual count" sensor (063-0172-004) turns a 720 into 1440. If you swap a standard sensor (063-0171-669) in place of a high-pulse one, divide the cal by 2; going the other way, multiply by 2. This is the single most common reason a rate is off by exactly half or double.
The catch test
Use water, and do it two or three times.
- Zero the total volume on the console.
- Spray a measured amount into a container you can read accurately.
- Corrected meter cal = current meter cal × (total volume the console counted) ÷ (volume you actually caught).
- Enter the new cal, and write it on the machine with a paint marker. Tags wear off.
Sanity check while you're there: (meter cal ÷ 10) × GPM ÷ 60 = pulses per second. A 720 cal at 100 GPM should be about 120 pulses per second.
Anhydrous: don't use the liquid cal
This one over-applies nitrogen by a factor of four. The flow meter tag has a separate NH3 cal in pounds of N — an RFM 60S reads 710 for liquid but about 168 for NH3. No tag? Divide the liquid cal by 4.22. Raven's current guidance suggests 190 as an NH3 starting point for the RFM 60S; either way, confirm with a catch test. And on NH3, don't run nurse tanks below 5%: an empty tank spins the turbine on vapor at high speed and wears the bearings.
Installation mistakes that look like a bad cal
- The 6-to-8 rule: you need 6–8 inches of straight pipe per inch of meter diameter ahead of the meter, or the swirl off an elbow gives bad readings. Mount horizontal or slightly uphill; vertical for very low rates.
- A meter installed backwards still pulses — erratically.
- A missing strainer lets debris slow or stop the turbine. Pull the meter apart and make sure the turbine spins freely when you blow through it.
- Running the meter outside its flow range (too low is the usual problem on a big meter at a small rate) makes it erratic.
Erratic rate: valve or meter?
Set a self-test speed and put the product in Manual. If the rate settles, the control valve is the problem. If it's still bouncing, it's the flow meter — or a bad boom switch, which you find by running the area/hour test one switch at a time.
The complete rate-control section, including valve cal digits, valve types and what a meter should read on each, is in the Raven Troubleshooting Guide. We keep Raven flow meters, sensors and strainers on the shelf — call (509) 838-2209 if you want a second opinion on a number before you change it.
Procedures summarized from Raven's Interactive Troubleshooting Guide and Raven Support Center articles. Confirm values against the manual for your hardware. Spray Center Electronics is an independent Raven dealer in Spokane, WA.