Mersen FSM Series Multi-Meter ...
IN STOCK (leaves warehouse same day if ordered before 3pm ET)
$68.86
Mersen FSM Series Multi-Meter Fuse, 1000VAC/1000VDC Ferrule

Mersen FSM Series Multi-Meter Fuse, 1000VAC/1000VDC Ferrule

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Model: FSM44/100

In Stock (leaves warehouse same day if ordered before 3pm ET)

$68.86
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Mersen FSM Series Multi-Meter Fuse, 1000VAC/1000VDC Ferrule

Mersen's FSM Series is a true 1000VAC/1000VDC fuse engineered to protect both analog and digital multi-meters in power electronics metering and controls applications. Built by Ferraz Shawmut, part of the Mersen family, these fuses feature a Ferrule connection/terminal type, a Midget fuse class body, and a Fast-Acting speed characteristic sized in the industry-standard 10x35/10x38 form factor. This particular rating is 0.44A, one of three amperage ratings offered across the FSM line to cover the full range of multi-meter fusing requirements.

Key Features

  • Compact Fuse Body: 10x35/10x38 dimensions for use in standard midget-class multi-meter fuse holders.
  • Durable Construction: GMG body/insulating material paired with Tin-Plated Copper connection/terminal material for reliable, corrosion-resistant contact.
  • Ferrule Connection: Ferrule connection/terminal type with Clip mounting for secure seating in standard multi-meter fuse blocks.
  • Dual AC/DC Rating: Rated 1000V AC and 1000V DC (AC/DC) for use across analog and digital multi-meter platforms.
  • Ampere Rating: 0.44A rating for precise circuit protection in power electronics metering and controls equipment.
  • High Breaking Capacity: 20 kA AC max interrupting rating (I1) for dependable performance under fault conditions.
  • Fast-Acting Speed: Fast-Acting characteristic supports quick response for sensitive metering circuits.
  • Frequency Compatible: Rated for 50/60 Hz operation.

Technical Specifications

  • Body/Insulating Material: GMG
  • Connection/Terminal Type: Ferrule
  • Connection/Terminal Material: Tin-Plated Copper
  • Mounting: Clip
  • AC or DC: AC/DC
  • Ampere Rating: 0.44 A
  • Frequency: 50/60 Hz
  • Fuse Class: Midget
  • Speed/Characteristic: Fast-Acting
  • AC Max I.R./Breaking Capacity (I1): 20 kA

Typical Applications

  • Analog and Digital Multi-Meter Protection
  • Power Electronics Metering Equipment
  • Instrumentation and Controls Market Devices
  • Test Equipment and Panel Meter Circuits

Why Mersen?

Mersen's Ferraz Shawmut FSM Series fuses are purpose-built for the demanding requirements of multi-meter protection, combining a GMG insulating body, Tin-Plated Copper terminals, and a 1000VAC/1000VDC dual rating with a 20 kA breaking capacity in a compact 10x35/10x38 Midget-class body. The Fast-Acting design and Ferrule termination make these fuses a dependable choice for professionals specifying reliable overcurrent protection in metering and power electronics controls equipment.

Manufacturer Resources

Mersen Product Catalog

Product Specs

list_batch:
MERSEN-20260825
Product Type:
Fuse
Product Material:
GMG
Connection Type:
Ferrule
Voltage Rating:
1000V
Product Finish:
Tin-Plated Copper
Series:
FSM
Department:
Electrical
Product Group:
Circuit Protection
Product Subgroup:
Fuses

Mersen FSM44/100 – Frequently Asked Questions

1) Will the Mersen FSM44/100 fuse fit a standard multimeter fuse holder?
The FSM Series fuse uses the 10x35/10x38 midget body, which is the size standard multimeter fuse clips and midget-class holders are built around. Termination is a ferrule with tin-plated copper contacts, and mounting is by clip, so it seats in standard multi-meter fuse blocks without an adapter.
2) Is the Mersen FSM fuse rated a true 1000V on DC as well as AC?
Yes, 1000V AC and 1000V DC both. That matters because plenty of small fuses carry a high AC number and a much lower DC number; the FSM is rated at 1000V on either. It is rated for 50/60 Hz operation and carries a 20 kA AC maximum interrupting rating.
3) What amperage is the Mersen FSM44/100 and why such an odd rating?
FSM44/100 is a 0.44 A fuse. Meter manufacturers size the low-current input leg tightly so the fuse clears before the shunt or input circuit is damaged, which is why the value is fractional rather than a round number. It is one of three amperage ratings in the FSM line covering multi-meter fusing needs, so match the printed value on the fuse you pulled out rather than rounding up.
4) Can I use a glass automotive-style fuse instead of the Mersen FSM in my meter?
No. Glass tube fuses such as the Littelfuse AGA and AGU series are low-voltage types and have neither the 1000VAC/1000VDC rating nor the 20 kA interrupting capacity the FSM carries. In a meter input that can see a fault at line voltage, a glass fuse can rupture instead of clearing. Stay with a 1000V-rated midget fuse of the correct amperage.
5) Is the Littelfuse BLF midget fast-acting fuse a drop-in replacement for the Mersen FSM44/100 in a multi-meter?
No. Both are midget-class fast-acting fuses, but the Mersen FSM44/100 is rated 1000V AC/DC with a 20 kA AC interrupting rating, while the Littelfuse BLF series is a 250V midget fast-acting fuse in a laminated tube. A handheld or bench multi-meter input circuit specified at 1000V needs the 1000V-rated FSM part; a 250V fuse does not carry the voltage withstand that meter-input protection depends on, even though it will physically seat in the same clip-mounted midget holder.
6) For protecting a panel-mounted energy meter rather than a handheld multi-meter, what should I look at instead of the FSM44/100?
The Square D PowerLogic energy meter fuse pack is sold as a set of three 0.5A 600V fuses intended for metering circuits on a PowerLogic energy meter, which suits a three-phase panel installation where you fuse all legs at once. The Mersen FSM44/100 is a single 0.44A fuse rated 1000V AC/DC, fast-acting, in a midget 10x35/10x38 ferrule body for the input circuit of analog and digital multi-meters. Choose by where the fuse sits: the PowerLogic set for the installed meter's voltage-sensing leads, the FSM for the instrument itself.
7) Fast-acting or time-delay for a multimeter input fuse?
Fast-acting, and that is what a meter input needs. The FSM Series is specified fast-acting so it opens quickly when someone puts the leads across a live circuit while the meter is still in current mode. A time-delay midget fuse of the same amp rating would let that fault energy through long enough to damage the meter, so do not substitute one.
8) Is this the same thing as a panel meter fuse pack like the Square D PowerLogic set?
Different job. The Square D PowerLogic energy meter fuse pack is a set of three 0.5A 600V fuses for protecting voltage-sense leads on an installed energy meter. The Mersen FSM is a 1000VAC/1000VDC fuse for the input circuit of analog and digital multi-meters and test equipment. Pick by the equipment you are fusing and the voltage the circuit can actually see.
9) Is Ferraz Shawmut the same as Mersen for fuse part numbers?
Yes. Ferraz Shawmut is part of the Mersen family, and the FSM Series is built under that lineage. If your meter documentation or an old spare calls out a Ferraz Shawmut FSM part, the Mersen FSM with the same suffix is the same fuse. For this one the part number is FSM44/100.
10) What is the difference between the Mersen FSM44/100 and a Littelfuse AGU or AGA glass tube fuse?
The Mersen FSM44/100 is a midget-class fuse in a 10x35/10x38 body with a GMG insulating body and tin-plated copper ferrules, rated 1000V AC/DC fast-acting with a 20 kA AC interrupting rating for multi-meter and metering circuits. The Littelfuse AGU and AGA parts are AG-style glass tube fuses, including the AGA5 at 5A. Glass-bodied AG fuses are a general-purpose automotive and electronics format; the FSM uses a filled, non-glass body specifically so it can interrupt high fault energy at meter-input voltages.
11) Can I use a Class CC time-delay fuse such as the Littelfuse CCMR040 in place of the Mersen FSM44/100?
No. The Littelfuse CCMR040 is a 40A Class CC time-delay fuse, built to ride through motor and transformer inrush in branch circuit applications. The Mersen FSM44/100 is a 0.44A fast-acting midget fuse rated 1000V AC/DC for metering circuits, where the point is to clear quickly and protect sensitive instrumentation. The amperage, the speed characteristic, and the fuse class all differ, and Class CC rejection-style mounting is not interchangeable with the clip-mounted midget holders the FSM seats in.
12) Will a Mersen FSM fuse corrode in a meter that lives in a service truck?
The ferrules are tin-plated copper, which resists corrosion and keeps clip contact resistance low, and the body is GMG insulating material. That combination is what keeps a low-current meter reading stable in a fuse that gets handled and stored in the field.
How fast can I get the Mersen FSM44/100 delivered?
Most orders ship the same day from our distribution partners, with quick delivery throughout the continental U.S. Need it urgently? Contact Us for expedited shipping options.
Can I return it if it doesn’t work for me?
Yes—ZenSupply offers a hassle-free return policy. If the product isn’t the right fit, reach out to our support team for a return authorization or setup a return by following our return instructions.
Does the Mersen FSM44/100 come with a warranty?
Absolutely. The Mersen FSM44/100 is backed by a manufacturer’s warranty. For full warranty terms, check the product documentation or Contact Us.
How do I get technical support or installation help for the Mersen FSM44/100?
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