OHAUS SPX421 Manual, Explained: Setup, Keys, Modes and Calibration

The SPX421 manual, made simple: set up the OHAUS Scout SPX421, use the four keys and application modes, and calibrate it with the included 200 g span mass. The 420 g x 0.1 g SPX421 is in stock at MNM Scales for $258.00 (regular $416.00).

The OHAUS SPX421 (item 30253024) is the 420 g x 0.1 g model in the Scout SPX portable-balance line. It is a compact classroom, lab, field and production-check balance with a backlit LCD, 1-second stabilization and a 4.7 in stainless pan. This page walks through the steps most users need from the official OHAUS Scout SPX instruction manual (P/N 30268991, revision C). Choosing a portable balance first? Start with our portable scale buying guide. Comparing OHAUS lines? See OHAUS Valor vs Ranger vs Scout. The 120 g x 0.001 g Scout has its own guide: the OHAUS Scout SPX123 manual.

SPX421 manual at a glance: specifications

Item	OHAUS SPX421
OHAUS item / model	30253024 / SPX421
Capacity x readability	420 g x 0.1 g
Repeatability (std. dev.) / linearity	0.1 g / 0.1 g
Stabilization time	1 s
Pan	Ø 4.7 in (120 mm), 304 stainless steel
Draft shield	No (used on 1 mg Scout SPX models only)
Display	Backlit LCD, 0.78 in / 20 mm digits
Modes	Weighing, parts counting, percent weighing, check weighing, totalization, display hold
Weighing units (this model)	g, ct, N, oz, ozt, dwt, grn and a custom unit. kg, lb and lb:oz are not available on the SPX421.
Calibration	External span or linearity. Span mass 200 g (included). Linearity masses 200 g and 400 g (the 400 g mass is not included).
Power	AC adapter (included) or 4 AA batteries (not included); typical battery life 120 hours
Operating temperature	50 °F to 104 °F (10 °C to 40 °C), 10% to 80% RH, non-condensing, indoor use
Dimensions / net weight	8.8 x 2.1 x 8 in (224 x 54 x 202 mm, L x H x W); 2.2 lb (1 kg)
Interface	Optional RS232, USB host, USB device, Ethernet or Bluetooth (sold separately)
Legal for trade	Non-NTEP
In the box	Balance, round pan, AC adapter, instruction manual and the 200 g span calibration mass

Other Scout SPX models in stock

The SPX421 shares its chassis, keys and menu with the rest of the Scout SPX line. If you want the same 420 g capacity at a finer 0.01 g step, see the OHAUS SPX422. If you want the same 0.1 g readability with more capacity, see the OHAUS SPX621. The milligram Scout is covered in the SPX123 manual. This page stays on the SPX421.

Model	Capacity x readability	Price
SPX421 (this guide)	420 g x 0.1 g	$258.00 (reg. $416.00)
SPX422	420 g x 0.01 g	$610.00 (reg. $1,056.00)
SPX621	620 g x 0.1 g	$322.99 (reg. $615.00)

Setting up the SPX421

1. Use the balance indoors on a clean, firm surface, away from drafts, rapid temperature changes, vibration and magnetic fields.
2. Release the red transportation lock on the sub-platform by turning the red pointer 90° counter-clockwise, to the unlocked position.
3. Set the round 120 mm pan straight down on the sub-platform.
4. Level it: turn the adjustable feet until the bubble sits in the center of the illuminated level window on the front. Re-level it whenever you move the balance.
5. Connect the included AC adapter to the jack at the rear, then to a compatible grounded outlet. To run on batteries, install four AA cells (not included) with the polarity marked in the compartment.
6. Press and hold On/Zero for one second to turn the balance on. It runs a display test, shows the software version and enters the active weighing mode. After power-on, warm it up for at least 5 minutes before you rely on a reading. Press and hold the same key until OFF appears to shut it down.
7. When you first install the balance, or after you move it, perform a span calibration with the included 200 g mass (see SPX421 calibration below).

A security slot at the rear accepts an optional cable lock (not included). The security switch on the underside must be in the unlocked position to calibrate or to change units; when it is locked, the Calibration menu is hidden and the current unit is locked.

Controls, modes and units

The SPX421 has four keys. A short press (under one second) runs the primary function; a long press (more than two seconds) runs the secondary function. In the menu, the same keys become Yes, No, Back and Exit.

Key	Short press	Long press	In the menu
On/Zero	Turns the balance on, or zeros it	Turns the balance off	Yes (accept)
Print	Sends the current value to an optional interface if Auto-Print is off	Units: steps through the enabled weighing units	No (next item / reject)
Function	Starts the current application function (for example, store a total or begin Hold)	Mode: changes the application mode	Back
Tare	Enters or clears a tare	Menu: opens the user menu	Exit (also aborts a calibration in progress)

Press and hold Mode to reach Weigh, Count, Percent, Check, Totalization or Hold. Weighing is the factory default: tare a container if you need one, then add the sample. In counting, you can build or reuse an average piece weight from a 5, 10, 20, 50 or 100 piece sample (press Function to view the current APW). Percent weighing compares a sample to a stored 100% reference. Check weighing compares a sample to stored low and high limits, including positive, negative and zero-check setups. Totalization stores a series of positive weights; Hold can capture the first stable reading (Display Hold, the default) or the highest stable reading (Peak Hold), each at or above 5d.

On the SPX421, the official unit table lists gram (420 x 0.1), carat (2,100 x 0.5), newton (4.119 x 0.001), ounce (14.815 x 0.005), troy ounce (13.500 x 0.005), pennyweight (270.1 x 0.1) and grain (6,480 x 2), plus a custom unit. Kilogram, pound and pound:ounce are not available on this model. Availability can also depend on region.

OHAUS SPX421 calibration

OHAUS recommends a span calibration the first time you use the balance, and again after you move it, so the reading stays accurate at the new location. Have the correct masses ready and set the security switch to the unlocked position before you start.

Span calibration (zero and span)

1. Press and hold Menu until the menu prompt appears, then release. When C.A.L is shown, press Yes.
2. When SpaN is shown, press Yes to start span calibration.
3. The display shows –C– while it stores the zero reading, then shows the calibration weight value (press No if you need to toggle the value).
4. Place the specified 200 g mass on the pan. The display shows –C– while it stores the span reading, then done if the calibration succeeded. The balance returns to the previous application mode.

To abort a calibration in progress, press Exit. If calibration fails, the balance shows CAL E: check that you used the 200 g mass, that the pan is clear at zero, and that the bench is firm and draft-free, then retry.

Linearity calibration (zero, mid-point and span)

From the Calibration menu, choose LIN instead of SpaN. Linearity calibration stores a zero, a mid-point and a span. For the SPX421, the official masses are 200 g and 400 g. The included 200 g span mass covers the mid-point; the 400 g mass is not included and must be supplied separately. Use both masses when you run a linearity calibration.

In-house or NIST calibration before it ships

The SPX421 is well under 2.2 kg, so it uses this service calibration tier. Add either option to the order and our TDA-registered technicians calibrate it in-house before it ships:

Service	Price	What you get
In-house calibration with certificate (NIST-tested weights)	$95.00	Certificate with the balance, using our NIST-tested weights
NIST calibration with NIST-traceable certificate	$395.00	NIST-traceable certificate with the balance

Add in-house calibration for $95.00 or NIST calibration for $395.00. See in-house vs NIST certificates if you are choosing a certificate level, and how to calibrate a scale for the general steps.

Already own an SPX421? We calibrate balances on-site across Houston and its suburbs at $295 plus $2 per mile round trip, and nationwide by mail with mail-in scale calibration, in-house or NIST. See how often a scale should be calibrated and what scale calibration costs.

NTEP status for the SPX421

The OHAUS SPX421 is non-NTEP. OHAUS lists Legal for Trade as not applicable on this Scout SPX model, and it is used for classroom, lab, field and general weighing rather than buying or selling by weight. If you need a legal-for-trade portable balance, here is an NTEP alternative: the OHAUS SJX1502N/E, 1,500 g x 0.01 g, NTEP Class II, $275.00 (regular $1,507.00), in stock. Setup for that model is in our OHAUS SJX1502N/E manual. Read what NTEP and legal for trade mean, or check a model with our legal-for-trade scale checker.

Error codes and a reset

If the display shows an error such as Err 8.3 (overload), Err 8.4 (underload, often a pan that is off the sub-platform) or CAL E (calibration did not complete), see our scale error codes guide for the Scout Err 8.x and CAL E list. This page does not repeat that table. To reset Setup, Mode or Unit items to factory defaults, use the Reset item inside that menu, or see the Scout reset notes in OHAUS Valor vs Ranger vs Scout.

Frequently asked questions

Where can I get the SPX421 manual?

A printed OHAUS Scout SPX instruction manual (P/N 30268991) ships in the box with the SPX421. This guide walks through the setup, keys, modes and calibration steps most users need from that manual. The same manual also covers other Scout SPX models, including the SPX123.

How do I calibrate the OHAUS SPX421?

Unlock the security switch, press and hold Menu until C.A.L appears, press Yes, then Yes on SpaN. Confirm the zero reading, place the included 200 g calibration mass on the pan, and press Yes if prompted. The display shows done when span calibration succeeds. MNM Scales, an authorized OHAUS dealer, offers in-house calibration with a certificate for $95.00 or NIST calibration with a NIST-traceable certificate for $395.00, nationwide by mail, plus on-site service in the Houston area at $295 plus $2 per mile round trip.

What calibration weight does the SPX421 use?

The official Scout SPX manual (Table 6-3) specifies a 200 g span mass for the SPX421, and that calibration weight is included with Scout SPX models up to 620 g capacity. Linearity calibration uses 200 g and 400 g; the 400 g mass is not included.

Is the OHAUS SPX421 NTEP?

The SPX421 is non-NTEP. Here is an NTEP alternative: the OHAUS SJX1502N/E, 1,500 g x 0.01 g, NTEP Class II, $275.00, in stock.

How do I set up the SPX421 for the first time?

Release the red transportation lock (turn the pointer 90° counter-clockwise), set the round pan on the sub-platform, level the balance, connect the included AC adapter or install 4 AA batteries (not included), warm it up for at least 5 minutes, and run a span calibration with the included 200 g mass.

What weighing units does the SPX421 have?

On this model the official unit table lists gram, carat, newton, ounce, troy ounce, pennyweight, grain and a custom unit. Kilogram, pound and pound:ounce are not available on the SPX421.