Short answer: for a 24 V supply drawing 0.25-1.0 A, fit a 1/16 DIN DC panel meter with a 48 x 48 mm [1.89 x 1.89 in] bezel in a 45 x 45 mm [1.77 x 1.77 in] square cutout, and order the 1.999 A current input with the shunt built in — the maximum draw then sits at half scale with 1 mA resolution. The meter's own bezel gasket seals the hole, and the door's rating runs only as high as the meter's front rating. That front figure decides whether a washdown door stays honest. You can mark and cut the square yourself in an afternoon, or we cut it factory-fresh and the box arrives cut, deburred and rated. The sections below pick the range, size the hole and list the checks that prove both the reading and the seal.
What you need
- A 1/16 DIN DC volt/ammeter with a dual display: 48 x 48 mm [1.89 x 1.89 in] bezel, a 1.999 A current input with the shunt built in, and a voltage input that spans past the rail.
- The supplied bezel gasket and two clamp brackets, which ship with the meter.
- A door or panel carrying the DIN square cutout, corners square and faces clean.
- A DMM or logging multimeter accurate to 0.5% or better at the full-load current, for the cross-check.
- Above about 10 A of continuous load, an external 50 mV shunt and a meter input that reads millivolts.
The range rule: twice the load
A panel ammeter reads best with the load around half of full scale. On the usual 3½-digit display, ranges step by tens — 199.9 mA, 1.999 A, 19.99 A — because each spans 1999 counts. The nominal value (2 A, 20 A) is what you size against. Pick the smallest range whose nominal full scale is at least twice your highest continuous reading. That gives headroom for load growth on one side and three useful digits on the other. An analog pointer meter follows the same logic with a class figure instead of counts. A full-scale draw on a 0-2 A, class 1.0 meter carries a ±0.02 A error, which is 2% of the reading at mid-scale. Combo meters put volts and amps in one bezel, so one cutout serves both readings.
Sizing the range for this supply
Inputs: a 24 V DC rail feeding a test load that runs 0.25 A at idle and 1.0 A at full (the case in front of you); a 3½-digit panel display stepping 199.9 mA, 1.999 A, 19.99 A; and a 50 mV full-scale burden assumed for the internal shunt — the output every standard DC shunt is built to, and the one figure to replace if your datasheet differs.
Rule: smallest range whose nominal full scale is at least twice the maximum draw.
Arithmetic:
- 2 x 1.0 A = 2.0 A nominal, which lands on the display's way of printing a 2 A range.
- Position on scale: 1.0 / 1.999 = 50.0%, with the 0.25 A floor at 12.5%.
- Resolution: 1 mA per count, so 0.250 A reads to ±0.4%.
- Burden: R = 0.050 V / 1.999 A = 25.0 mΩ; at full load the meter drops 25.0 mV, which is about 0.10% of the rail, and dissipates 25 mW, rising to 0.10 W at full scale.
- Voltage: the 199.9 V input shows 24.0 V in 0.1 V steps, 0.4% of the reading.
Result: order the 1.999 A input with the shunt inside; no separate shunt at this load. Decision: that input carries any continuous draw up to 1.0 A. The same rule moves a growing load — 1.0 A to 10 A continuous — up to the 19.99 A input, where the low draw sits at 5% of scale and each count widens to 10 mA. Draws under 0.1 A drop to the 199.9 mA input for ten times finer steps. At 0.25-1.0 A, this input is the order line.
When the shunt lives outside the meter
Meters with the shunt built in usually stop around 5-10 A, the sizes catalogs stock. Past that the shunt is a separate part in the current path, built to deliver 50 mV at rated current, with standard ratings up to 500 A and 0.5 accuracy class. The 20 A size mounts on 35 mm DIN rail under an insulating base and cover.
Size it by the same twice-the-load rule plus the shunt makers' continuous-duty guidance, which caps running at about two-thirds of rated current. A continuous 15 A load then takes a 30 A, 50 mV shunt. R = 0.05 V / 30 A = 1.67 mΩ, the drop at full current is 25.0 mV, and the heat is 15 x 15 x 0.00167 = 0.38 W. Put it in the negative return so a ground-referenced meter input sits within tens of millivolts of earth; a high-side shunt needs an isolated input.
The cutout and what keeps the rating
If you want the fundamentals first, the guide to cutouts, glands and HMI windows carries them. DIN 43700 fixes the bezel sizes and the panel cutouts that suit them:
| DIN size | Bezel | Panel cutout | Bezel lip per side |
|---|---|---|---|
| 1/32 | 24 x 48 mm [0.94 x 1.89 in] | 22 x 45 mm [0.87 x 1.77 in] | 1.0 mm |
| 1/16 | 48 x 48 mm [1.89 x 1.89 in] | 45 x 45 mm [1.77 x 1.77 in] | 1.5 mm |
| 1/8 | 96 x 48 mm [3.78 x 1.89 in] | 92 x 45 mm [3.62 x 1.77 in] | 2.0 mm |
| 1/4 | 96 x 96 mm [3.78 x 3.78 in] | 92 x 92 mm [3.62 x 3.62 in] | 2.0 mm |
The 1.5 mm lip per side is the whole sealing idea. The supplied gasket compresses between bezel and door face on that bearing, so keep both faces bare and burr-free. Typical 1/16 DIN clamps grip panel thickness from 0.5 to 6 mm — the datasheet prints the range — and 16 ga stainless sheet at about 1.5 mm [0.059 in] sits well inside it. Behind the door, case plus terminal block runs roughly 75-100 mm [3.0-3.9 in] on common models, so leave that depth clear before you fix anything to the inner face.
Every penetration sets its own ceiling, and the lowest one wins: a door cut for a meter is rated at the meter, not at the box. The NEMA 4X vs IP66 comparison works this through. Most 1/16 DIN meters carry an IP65 front; some carry IP66, printed on the nameplate. Our boxes are rated NEMA 4X / IP66 by the manufacturer; not UL listed. An IP65 front caps the door assembly at IP65, so for washdown you order the IP66-front meter or keep the display behind a window. The cutout designer covers getting a tight seal on a panel instrument cutout.
Order the cutout with the box while the door is still on the drawing. The cutout designer lays the DIN square on any face, and the enclosure arrives deburred and rated, delivered in 10 business days from your order (from drawing approval on custom work).
Fitting the meter: nine steps
- Confirm the cutout on your meter's datasheet before marking anything: DIN 43700 puts the 1/16 hole at 45 x 45 mm, but a few models move a millimetre.
- Mark the square with the panel cutout layout template so the edges sit parallel and square to the door, centred where the display reads without glare or a reach.
- Cut it with the method the clean-square-cutout comparison ranks for your tools and the sheet gauge.
- Deburr both faces and wipe them down; a hairline burr under the gasket leaks.
- Seat the supplied gasket square on the bezel, dry and untwisted.
- Insert the meter from the front, gasket outward, leads trailing behind.
- Fit both clamp brackets finger-tight, then alternate corners a quarter turn past gasket contact, until the 1.5 mm lip bears all round.
- Wire the current path in series with the load through the A terminals; on a combo meter, take the voltage sense from the load side so the display shows what the load sees, past the meter's own 25 mV drop.
- Power the meter from the same rail when its supply window covers it, then run the checks below.
Checks before you close the door
- Current: series the DMM at full load and compare — meter and DMM agree within ±0.01 A, which is 0.5% of the chosen scale.
- Voltage: the two displays agree within the 0.1 V step at 24.0 V.
- Burden: supply terminal minus load terminal reads about 25 mV at the maximum draw — the example's figure, live on your wiring.
- Gasket line: even compression all round the square, and the latch closes without pushing the case.
- Gross leak: a one-minute bench mist around the bezel catches a misplaced gasket; the washdown rating itself rests on the meter's front figure, and IEC 60529 tests IPX5 with a 6.3 mm nozzle at 12.5 L/min from 2.5 to 3 m — no spray bottle matches that, so the nameplate carries the duty.
Mistakes that cost the rating or the reading
- An IP65 front on a washdown door caps the whole assembly at IP65; the lowest-rated penetration wins, so order the IP66 front when the hose is part of the shift.
- Swarf or a burr left in the cutout seats under the gasket; if the hole came out small or ragged, enlarging the door cutout without swarf damage rescues it.
- Clamps cranked hard bow the bezel and lift the gasket mid-side; a quarter turn past contact is the whole job.
- A shunt in the positive leg with a ground-referenced meter offsets the reading; keep it in the negative return or specify an isolated input.
- A meter swapped out later leaves an unrated square; close it with a rated blank DIN cover that carries the door's figure, or send a revised cutout drawing for a custom door that keeps the layout you actually need.
For the bench case, the whole decision is three lines: the 1.999 A input for the 0.25-1.0 A load, the 45 x 45 mm square with the supplied gasket, and an IP65 front indoors or an IP66 front wherever the hose lives. When you lay out the whole panel, the enclosure builder places the meter beside glands, pushbuttons and DIN rail in one drawing.
Catalog dimensions to compare
Compare these catalog dimensions with your component layout. Open each enclosure for its rating, material and usable space, then check those specifications against your application.
| Enclosure | Material | Outside H x W x D / display | Rating |
|---|---|---|---|
| 12 × 10 × 6 in | 304 stainless | 12 x 10 x 6 in | Rated NEMA 4X / IP66 by the manufacturer; not UL listed |
| 16 × 14 × 8 in | 304 stainless | 16 x 14 x 8 in | Rated NEMA 4X / IP66 by the manufacturer; not UL listed |
| 20 × 16 × 8 in | 304 stainless | 20 x 16 x 8 in | Rated NEMA 4X / IP66 by the manufacturer; not UL listed |
Questions
What changes if the load spikes above 2 A during the test?
Short overload tolerance past the range is a datasheet figure, so read it there. Without that headroom, the 19.99 A input still covers the test, but each step widens to 0.01 A and a 0.25 A reading moves in 4% jumps. For spikes that repeat every cycle, a 50 mV external shunt sized by the same twice-the-load rule reads them without changing ranges.
How accurate is the current reading at full load?
On the chosen input, a 0.5%-of-scale meter is good for ±0.01 A, which is ±1% of a 1.000 A reading. A separate 0.5-class shunt stacks another ±0.01 A at half load, so the paired worst case is about ±2% of reading. A 0.1%-class meter cuts its own share to ±0.002 A, about ±0.2% of the reading.
Can one meter show volts and amps together?
Yes; dual-display DC meters fit a voltmeter and an ammeter in one 48 x 48 mm case sharing a single square cutout. Their electronics usually draw power from the measured rail across a window of roughly 4-30 V, which a 24 V rail satisfies while it is being measured; a separate low-voltage feed suits rails outside that window. The datasheet prints the exact window.
Should I cut the hole myself or order it cut?
Order it cut when the door is still on the drawing: the cutout designer places the square, checks spacing to folds and hinges, and the enclosure arrives deburred, rated and delivered in 10 business days — counted from your order, or from drawing approval on custom work. A shop cut costs a layout, a nibbler and a careful deburring pass, and the rating rides on how clean that gasket seat comes out.
